Optimus Prime - Toshiyuki Morikawa: Beast Wars Metals Jaguar (Ravage)
Megatron - Keiji Fujiwara: Beast Wars Dinobot, Micron Densetsu Devastor (Armada Scavenger), Animated Grimlock
Ratchet - Tatsuo Tobita: No TF roles
Bulkhead - Takashi Nagasako: Isaac Sumdac, Animated Snarl, Animated Brawn
Arcee - Shizuka Itō: No TF roles
Starscream - Satoshi Tsuruoka: Beast Wars Neo Strada
Cliffjumper - Noriaki Sugiyama: No TF roles
Jack Darby - Jun Fukuyama: No TF roles
Raf Esquivel - Motoko Kumai: No TF roles
Miko Nakadai- Nozomi Furuki: No TF roles
William Fowler - Kenji Nomura: No TF roles
June Darby - Hitomi Nabatame: No TF roles
So, we got some who have experience with the Transformers, and some who have been part of mostly non-TF anime.
But, yeah, it's too bad there's no Tesshō Genda for Optimus (they even got him for Omega Supreme and G1 Convoy in the Japanese dub of Animated. Yes, that's right, G1 Convoy/Optimus Prime made an appearance in the Japanese dub of Animated
Or even Seizō Katō for Megatron. Correct me if I'm wrong, but he isn't really doing much voice work these days, right?