They don’t need those roles at all do they?
It’s not like the Episode VII will pick up right where Episode 6 left off. It can’t UNLESS they re-cast the roles.
Which, now that you mention it. Might not be a bad idea.
It will likely take place right during or after the real fall of the empire. I just hope they don’t destroy the timeline of the books, which I don’t believe Lucas would allow.