Healers have a reduced chance to engrave a given character in the dust correctly, because of the stereotype about doctors having terrible handwriting.
Cavemen have a lot of experience traversing tight spaces in caves, and thus are always able to squeeze through a diagonal space (except possibly in Sokoban).
Alternatively, they are able to squeeze through diagonal spaces while carrying much more weight than other roles.
Monks are given some benefit or ability that enables them to get more benefit out of the ring of increase damage. This could be:
Rogues wearing the randomized “fencing gloves” should be able to sell items to shopkeepers which they have stolen from somewhere else at full price, as a pun on “fencing” stolen goods.
Ravens are always generated peaceful for Valkyries (or maybe only neutral Valkyries, since they follow Odin).
Rogues automatically see rings as “low value”, “moderate value”, or “high value”, roughly (but not exactly) corresponding to their base price.
Knights get an additional Wisdom-based saving throw against foocubi removing their clothing, flavored as keeping their virtue.
Archeologists automatically see a semi-randomized description of the quality of any mummy wrapping that comes into their inventory (“excellent specimen”, “wretchedly poor”, “slightly damaged”, etc). This gives them a clue as to its enchantment and beatitude.
Convicts can sometimes pacify the Rat King by chatting to him, similar to how they can tame rats by chatting.
Healers can use a stethoscope on a corpse to usually find out what its cause of death was.
A Priest in good standing with their god and standing on or near a coaligned altar sometimes has the ability to use a special spell or prayer to call a coaligned Angel to fight with them as a pet.
Monks should receive a benefit for fasting. This could be in the form of giving them a point of alignment record every so often when they are Hungry or worse, and/or slowing down their hunger rate when they are Hungry.
If you are a Ranger, your pets will specifically seek out missiles you have thrown which are lying on the floor, pick them up (perhaps even collecting multiple ones at a time) and bring them back to your side.
Samurai who twoweapon a katana and wakizashi should get some small bonus to damage or alignment record or similar. Though since they start the game able to do this, it would have to be a small bonus.
Barbarians do not require a saddle to ride tame monsters.
Cavepeople can safely sacrifice same-race monsters to “give them to the ancestors”, but only if the monster wasn’t killed by the player.
Buff Cavepeople by giving them a direct boost to carrying capacity beyond what they get from their Str and Con, to the point that they can carry more weight than any other role.
Priests get buffed effects from the invocation artifacts:
Cavemen wielding clubs get damage bonuses that increase with their skill in club, to make up for clubs’ awful damage.
Monks have ki-empowered strikes, which means they can strike incorporeal beings such as shades bare-handed.
Monks get shorter cooldowns for techniques as their experience level increases, to a minimum of 50 turns.
Convicts get an alignment bonus by writing graffiti. (Graffiti has to come from a magic marker, or a felt marker in variants that have it.)
You can use booze potions to clean off your wounds, helping you recover faster. Poison wounds, specifically, though this is debatable because 1) the game doesn’t track wounds you got from poison and 2) alcohol can help treat infections, whereas poison isn’t an infection.
Healers should probably be able to do this more successfully than other roles.
Priest characters can sacrifice gold at a coaligned altar for identical benefits as they would get from donating to a priest. The altar does not have to be attended.
Rangers have a special bonus towards searching for pits.
Archeologists and Tourists get experience for photographing monsters they haven’t yet photographed.
Certain roles have a small set of monsters that they can tame through non-magical means (such as Valkyries and winter wolves).
Different roles have different speeds for putting on armor, because they have varying amounts of practice with it. In particular, combat-heavy roles such as Barbarians, Valkyries and Samurai should continue to use the existing armor delays, whereas roles like Archeologists and Tourists should take longer to wear armor pieces.
Barbarians who roll a 1 on their damage die get the die rerolled and the second result used.
Barbarians get extra nutrition from eating corpses, since they have practice in how to eat them properly. Possibly up to 1.5x the nutrition.
Priests can hit incorporeal monsters like shades by default. Their attacks never pass harmlessly through.
Wizards start the game knowing the appearances of several random scrolls, rings, potions, and wands, but don’t actually have them in starting inventory.
Some special minor effect if you are wearing an ornamental cope as a Priest.
Archeologists can give artifacts to Lord Carnarvon. At the end of the game, any artifacts in his inventory count towards the game score, without having to drag them up to the Astral Plane.
Valkyries always get the snow boot bonus while walking on ice (i.e. they never stumble), even if they aren’t wearing snow boots.
Rangers have a role bonus which decreases the overall probability a projectile will break.
Rangers have a significantly better chance than other roles at untrapping beartraps (perhaps even just 100%).
Rangers get an alignment bonus for disarming naturally-generated bear traps, or possibly for catching a hostile monster in a player-set bear trap.
The Arch Priest specifically offers to open up a magic portal to the Plane of Earth if you talk to him with the Amulet of Yendor, as a Priest benefit, to skip the last dozen or so levels of the Dungeons of Doom.
For role differentiation: each role can only learn up to a certain number of spells. Wizards can learn them all, while roles like Healers can learn about a dozen; valkyries might be able to learn 3 and barbarians 1 (or 0). Possibly combine this with #2084.
Archeologists can apply their whips to cross over a ground-based trap with impunity, a la Indiana Jones.
Monks can gain intrinsic immunity to just about everything by leveling up, but most of these are nullified if the monk is wearing body armor.
When a Priest is gifted an artifact weapon, they are unrestricted in its skill and their skill cap in it is set to Skilled, rather than Basic.
Archeologists can ascertain a rough estimate of an item’s sale value without a shop handy, due to their profession.
Priest characters are allowed to choose the pantheon of gods they follow. This gives them Basic proficiency in one or two of the skills of that pantheon’s corresponding role.
Monks get a small amount of free bonus movement points when they kill a monster bare-handed, and also gain a small amount of free bonus movement points while making movement actions and not wearing body armor.
Samurai can wield katanas, wakizashis, and sabers in zero turns.
Cavemen (maybe only lawfuls) get a small alignment bonus for cannibalism, because it is honoring the ancestors.
Archeologists (maybe gnomes too) start the game with all valuable and worthless gems (but not gray stones) identified. If this is too powerful, perhaps they only begin the game with all worthless glass identified.
Monks can forcefight or kick boulders and break them with high enough Strength.
Rogues get backstab bonus against any incapacitated enemy (sleeping/paralyzed) in addition to fleeing ones.
If you are a Caveman, you get telepathy or clairvoyance while you are hallucinating.
Priest characters get sanctuary in rooms containing unattended coaligned altars, even though they aren’t temples.
Rangers can chat to certain animalistic monsters to calm them and make them peaceful (but not tame). Possibly generalize this into a skill that can be achieved by Cavemen, Monks and Tourists too.
Cavemen get a large damage/to-hit bonus when throwing spears at large mammals, or an alignment bonus for killing large mammals with spears.
Healers can use an uncursed unicorn horn as if it’s blessed. They could also get the unicorn applied passively every turn as long as it’s wielded (with or without gloves on).
Rogues can build and set traps, more types of traps than just plain pits and land mines and bear traps. Traps may consume some types of items to be set, like a sleeping gas trap will consume potions of sleeping. This should probably not be totally reversible through untrapping. Intended so the player can pick their battles and set up traps in an advantageous position.
Rogues have a 20% (or 10%, or whatever is balanced) chance of stealing a random lightweight item (say, less than 5 aum, or less than 20 aum to include potions) out of a monster’s inventory with every successful melee hit they make. This chance is increased if they are hitting with no wielded weapon or have no secondary weapon or shield, and maybe should scale with experience level too.
Other priest benefits: the chance of receiving a sacrifice gift is doubled, make it easier to get crowned or other high boons, the prayer timeout isn’t increased when crowned.
Priests can sacrifice corpses anywhere, with no need for an altar, except in Gehennom. (This should be strictly worse than altar sacrifice - maybe it only reduces prayer timeout, by less than it would normally, and can’t result in gifts.)
Valkyries only gain wings (and therefore flying) after they are crowned.
New type of book “encyclopedia”:
Valkyries can fly at will with the #fly command, but it costs Pw per turn/flying action to maintain.
Archeologists should be immune to rolling boulders.
Valkyries offering fire giant or frost giant corpses get double the sacrifice value. Possibly this could be generalized to other roles sacrificing “enemy” monsters.
Valkyries have some drain life power, as they are “choosers of the slain” in Norse mythology.
High level (maybe only XL 30) monks can get enlightenment by sitting on normal floor.
Samurai have an ability (maybe a special ability) to displace hostiles.
Knights pass over monsters in their way when doing a knight’s-move jump.
Knights instakill by checkmating all “king” monsters that are a knight’s-move away and are surrounded or cannot move.
80% of locks on containers, determined by the object id of those containers, can’t be opened by a credit card because they’re a latch or padlock or something that can’t be jimmied open. Perhaps Tourists get a bonus that allows them to open more locks.
Cavemen get a berserking bonus if their pet gets killed.
Roles which are good with melee weapons (Bar, Val, Kni?, Cav?) should be able to see the enchantment of their weapon after using it for a while, or perhaps right when wielding it. Alternatively, seeing the enchantment of a weapon should be based on skill: basic will reveal enchantment on 1% of hits, skilled on 10%, expert as soon as you wield the weapon.
The scroll of detect magic shows magic fountains on the level as well as magical items. Fountains discovered this way are then displayed as “magic fountain” when near or farlooked. Wizards can see them as magic fountains already without needing to detect magic.
