Joining the previously announced Kevin Conroy as Batman, Dana Delany as Lois Lane, Ron Perlman as Deathstroke, C. Thomas Howell as Professor Zoom / Reverse Flash and Vanessa Marshall as Wonder Woman are Justin Chambers as The Flash, Cary Elwes as Aquaman, Michael B. Jordan as Cyborg, Sam Daly as Superman, Nathan Fillion as Green Lantern, Danny Huston as General Lane and Kevin McKidd as post-Flashpoint Batman.
Here's the official plot summary for Justice League: The Flashpoint Paradox:
"When time travel allows a past wrong to be righted for The Flash and his family, the ripples of the event prove disastrous as a fractured, alternate reality now exists where a Justice League never formed, and even Superman is nowhere to be found. Teaming with a grittier, more violent Dark Knight and Cyborg, Flash races to restore the continuity of his original timeline while this new world is ravaged by a fierce war between Wonder Woman's Amazons and Aquaman’s Atlanteans. With breath taking action and an all-star voice cast, it's a bold, emotional vision that will forever change the landscape of the DC Universe."
Justice League: The Flashpoint Paradox is set for release on July 30th.