Sorry you can't do that. You have to use the role card that came with the caracter. That has already been confimed in another thread.
No, the Character cards and Role cards must stay together. This is from the Card Guild PDF:
You may substitute any character of the appropriate class
(along with a matching role and token card) from a base
set or Character Add-On Deck.
Given that the role card overlays the powers of the character card, your powers would suddenly change outright upon applying the role. Interesting, yes, but not very practical.