Libramarian
Adventurer
AD&D 1e's encounter reaction rolls take an interesting approach: the DM rolls for the basic disposition of NPCs upon encountering the PCs, and then works that into the roleplayed conversation. High Cha PCs walk around the gameworld finding most NPCs to be friendly and helpful -- whatever advantage they get out of that is largely determined by roleplay alone (the DM might roll reaction again if the conversation has boiled down to a particular binary breakpoint, where the result isn't obvious in context).That's the traditional approach in most games when trying to "encourage RP." You sell your RP to the DM, if he buys it, you get a bonus to the roll.
Aside from the 'gaming the DM aspect,' which is inevitable regardless of system, the thing I dislike about it is that it leads to big story/RP disconnects.
Player 1 RPs a diplomacy check. His character is supposed to be pretty good at diplomacy, and he makes a very compelling case, eloquently and appropriately in-character. Then rolls, with his '+2 for good RP,' and the die comes up 1.
Player 2 comes up, having not really been paying much attention and says something vaguely inappropriate to try to convince the same NPC. DM chucks the book at him with a -5 penalty. Natural 20.
If the RP is so immersive that the character's ability shouldn't matter, why even have the die roll? If we're trying to RP the character's abilities, why not wait until after the the die roll to see how well you do, then RP the results - at least you'll never get a huge disconnect like that.