Me, I can RP fairly well (or so the one other person I've RP'd with says). I'm just a bit post-shy at times. Well, more than a bit.
Though the only RP experience I have is from a pair - One that I made myself (partially original sci-fi RP) and a faction RP for a browser-based game I play...the latter died with the faction, and the former's only got two people - myself and one of my F2F friends...