Is it true that some of your characters have come from role playing games?
Just kidding. And just to be sure we're on the same page, you are talking about table-top RPGs, right, not the weird stuff between consenting adults? (Because in that case, the answer would be no. *grins*)
A few examples, the entire cast of Last Chance School for Girls comes from characters created for the Cyber Age Adventures Role Playing Game. And the character Frique, from my short story, "Angels of Their Better Nature," (collected in Show Me a Hero, both in trade paperback and ebook) originated in one of three Play by Email (PBeM) RPGs I once ran for a year or so for iHero Entertainment.