Everybody plays multiple roles -- idols and just plain folks alike. Idols are definitely more aware of their roles, give them a lot more conscious thought and attention, and play them up much more, but I think it's much easier to put together that kind of ongoing public-persona role out of personal qualities that you already have, rather than making it up out of whole cloth, or carrying out an arbitrary role-assignment from management (although I'm sure those things happen).
Just thinking of the people I know personally who maintain public personas (and I'd definitely include myself -- hey, I
do live in Southern California, after all, and one of the basic facts of life here is that you're always on stage
), I'd say that just about everybody's persona is constructed out of personal qualities -- emphasized, exaggerated, trimmed, decked out, prettied up or uglied down, but based on something inside.
It isn't always the case, of course, but there's generally a difference between clearly defined character-roles such as Haddo Gay, on one hand, and the ongoing public personas that so many people who are or want to be in the public eye adopt.
So -- I don't know. But there usually is a difference between a persona and "just a role".
If madness made us strong, we would all be invincible.