Though I find it more likely that Demandred would pose as a new noble adviser or general and just control Roedran. Generally it's rather difficult to play a well know person and the Forsaken tend to create new identities. We also know that Demandred likes to use proxies. In any case, I think Demandred's clothes also point to him being a Murandian noble. Maybe he also uses the Murandian House Chiendelna, which Luc names as his House.