TFW2005.com and TFormers.com have both received a press release containing details on the story and voice actors for Transformers Prime.  TFormers sister site ENewsInternational actually received the full list of credits which includes Dwayne "The Rock" Johnson as Cliffjumper.

MAIN CHARACTERS

AUTOBOTS

Optimus Prime - Peter Cullen
Arcee - Sumalee Montano
Bulkhead - Kevin Michael Richardson
Ratchet - Jeffrey Combs
Bumblebee - Rumored as Josh Keaton
Cliffjumper - Dwayne "The Rock" Johnson (More Info)

DECEPTICONS
Megatron - Frank Welker
Breakdown - Adam Baldwin
Knockout - Daran Norris
Starscream - Steve Blum

HUMANS
Jack - Josh Keaton
Miko - Tania Gunadi
Raf - Andy Pessoa
June - Markie Post
Agent Flower - Ernie Hudson 

THE SHOW

The Transformer saga continues as Optimus Prime and the Autobots battle the evil Decepticons, led by Megatron. With the future of the human race hanging in the balance, three young teenagers become critical in helping the Autobots prevent the Decepticon Army from conquering Earth. Prepare to experience the world of Transformers like never before.

The Transformer franchise sees the triumphant return of the Autobots characters to television in cutting edge computer-generated animation. The series both deepens the epic mythology of Autobots and Decepticons, while starting fresh for a new generation of viewers and future Transformers fans. With a bold and modern new look, Optimus Prime, Bumblebee and others are back to roll out against Megatron’s latest plots to conquer Earth. The Autobots may be few against the Decepticons menace, but they find increased strength here on their home away from home via bonds they've forged with three human teenagers. Make no mistake, the Transformers series will deliver heavy metal action and nail-biting suspense

Produced by Hasbro Studios

PRODUCTION CREDITS

Developed for Television By:
Alex Kurtzman
Roberto Orci
Duane Capizzi
Jeff Kline

Executive Producers:
Alex Kurtzman
Roberto Orci
Jeff Kline

Supervising Producer: Duane Capizzi

Supervising Animation Producer: Therese Trujillo

Producers:
Steven Puri
Mandy Safavi

Staff Writers:
Nicole Dubuc
Marsha Griffin
Joseph Kuhr
Steven Melching
Supervising Director: Dave Hartman

Music By: Brian Tyler

Main Title Theme By: Brian Tyler