Every pen-and-paper RPG has mechanical support for roleplaying built in. All you have to do is look at the character sheet.
For me, roleplaying means imagining how a character would behave in a fictional world. Mechanical details on a character sheet shape how a character is role-played because those notes help determine what is easy, what is hard and what is possible. I’m not saying every RPG handles this the same way. Burning Wheel and Pathfinder provide far different types of support for roleplaying. But pretending that one doesn’t offer support while the other does would be overlooking how all the rules impact roleplaying.
Consider these two Pathfinder characters — Bob has a good armor class and a high number of hit points while Joe has a poor armor class and low number of hit points. Would you role-play these characters the exact same way in all situations? Probably not.
But even if you did, the way everyone else in the setting would behave toward your character would be different. Bob going out to confront a giant might be considered brave, but Joe doing the same thing would be called foolhardy. And since character interactions build off of each other, it is not possible to always play Joe and Bob the exact same way.
Now consider a character made in Burning Wheel. The player details Instincts and Beliefs that mechanically denote the motivations and ethics of the character. The gamemaster crafts situations that challenge these core parts of the character to see what happens. As the character changes, the gamemaster adapts situations to poke and prod for more reactions.
This feedback loop, where gameplay and roleplay tie directly to things written on the character sheet, is built directly into the rules. But what prevents a gamemaster from doing the same thing in Pathfinder or any other RPG?
Nothing, except that writing out a background that includes those motivations and ethics is an optional part of play. Many GMs have used informal house rules to encourage similar opportunities for years. The major difference in play comes from how many things outside of the character sheet’s feedback loop can influence play at the table.
When thinking about these differences, I divide these different RPG mechanics into hard and soft roleplaying cues. Concepts like class or background or even a list of skills are soft cues on how to roleplay a character. A soft cue can be ignored freely but often is used to form the skeleton of a character. A Wizard with skill points in Track probably is a much different character than a Wizard without that skill.
Hard roleplaying cues tend to be difficult if not impossible to ignore and likely involve some form of enforcement by the gamemaster. Some examples here include a Paladin’s alignment or an Aspect of a Fate character. Both of those mechanics can be changed during play, but there are specific rules for how to do so (often involving GM approval) because of hard limits. Those mechanical bits exist to support other structures within the ruleset.
That’s part of the reason alignment has sparked so many discussions about Dungeons & Dragons over the years. Alignment can be a soft cue for most classes, but a hard cue for those who derive specific mechanical benefits from the structure. Which is why some players avoid certain classes — those players dislike the idea of someone saying they are roleplaying “wrong.”
A soft cue doesn’t require adjudication, but a hard cue often does. And there is a tendency to challenge and poke at the hard cues, or else why write them down? Your character has One Arm? Looks like there will be lots of ladders to climb!
There is a tendency to ignore the impact of soft roleplaying cues because they have always been there. But take a look at how many games rename the “Thief” just to add emphasis that the role involves more than just taking stuff. So baked-in assumptions become another thing some GMs talk with the group about before play begins. Or that’s something covered by more general rules like “Don’t be a jerk.” Of course, the behavior of jerks can be defined differently depending on who’s doing the defining, so hopefully someone will write the specifics down for anyone who comes in later.
So once again we come back to the rules and notes that are written on the character sheet. The only question is how many of these a particular group feels should come from the rulebook and how many come from talking to each other like equals. A group must find its own balance, regardless of the game being played.