well most of the voices are done by some big names out there for example heres some of the main character voices:

Katie Mulgrew as Flemmeth (Captain Janeway, Star Trek Voyager)
Tim Russ as Zathrian (Commander Tuvok, Star Trek Voyager)
Claudia Black as Morrigan (Aeryn Sun, Farscape)
Simon Templeman as Loghain Mac Tir (though he has done TV in the past, he has mostly been known for being a voice actors in games for most of the current generation of gamers history)
Steven Jay Blum as Oghren (Again not really known for himself but anyone who watches Marvel Xmen cartoon will recognize him as Wolverine!)
Steve Valentine as Alistair (PS3 fans will possibly recognize him for his work on Uncharted 2)
Jon Curry as Zevran (he's again famous more for games though I have a hard time finding info)
Mark Hildreth as Sten (Famous for being DJ Atomica in Burnout Paradise City and sounding a lot like Ryan Seacrest)
Keith Szarabajka as First Enchanter Irving (Seriously since Blackdawn in '96 this guy has been in so many games including saints row 2 and other big games)

The voice cast of this game is seriously just an amazing group of people. These are just main characters in the game.