Role playing, in the sense of what it's meant to be, has very little to do with the actual PVE world. You can make it as such, but really it gives you the opportunity to leave the game story and create your own.
You won't be limited by joining an RP server, but RP server populations are typically smaller than PVE and PVP servers due to less players over all partaking in role playing.
What a RP server will provide you that other servers do not, is a community of people who, while playing, envelope themselves into their character and their game. There are also chat rules most RPers live by and most of them will be happy to help you with them. Basically, you're acting out a story. You're character creation doesn't end when you choose a name and start the game, it only begins. After that, you'll need to create an entire character bio, and become that character in game. And other people will be doing the same. It can truly make for the best MMO gaming experience possible. The game no longer becomes finding a friend to grind out quests, but creating your own, and ultimately writing your own story as you go along.
If you're just playing the game normally, doing your own thing, grinding out quests and talking to people as if they're sitting behind a computer screen, then an RP server isn't for you. That is not role playing. That's just playing.