From the announcement over at StarWars.com:
"Actors John Boyega, Daisy Ridley, Adam Driver, Oscar Isaac, Andy Serkis, Domhnall Gleeson, and Max von Sydow will join the original stars of the saga, Harrison Ford, Carrie Fisher, Mark Hamill, Anthony Daniels, Peter Mayhew, and Kenny Baker in the new film."
You can scope out their IMDB pages for each actor below... Max Von Sydow! I can see him being a pretty badass Sith Lord.
Joining the original cast of: