From the Gameinformer website, which seems to be doing a lot of work promoting this game...
Peter Cullen - Optimus Prime
Greg Berger - Grimlock
Nolan North - Bruticus, Cliffjumper and Brawl
Troy Baker - Jazz, Jetfire, and Kickback
Fred Tatasciore - Megatron, Ratchet, and Metroplex
Steve Blum - Shockwave, Swindle, and Sharpshot
Isaac Singleton - Soundwave
I think they managed to keep most of the original WFC Voice Actors.