From what I can see on the net the game uses a cast of British voice actors and it will be the same for the North american version too. Never heard of any of these people myself but here's the full list:
Zael - Jack Ryder
Calista - Alix Wilton Regan
Yurick - Colin Ryan
Syrenne - Kelly Wenham
Mirania - Montserrat Lombard
Lowell - Derek Riddell
Asthar - Tom Goodman Hill
Therius - Daniel Curshen
Arganan - Peter De Jersey
Jirall - Blake Ritson
Zangurak - Nick Boulton
Zesha - Josh Cohen
Zepha - Antony Byrne
Outsider - Jo Wyatt
Ariela - Maria Darling
Warren - Lizzie Waterworth-Santo
Kentis - Antony Byrne
Horace - James Daniel Wilson
Meredith - Jo Wyatt
Zoran - Rupert Farley
Yurick's father - Tim Watson
Zael's mother - Louiza Patikas
Jeffery - John Voce
Narrator - Chris Fairbank
Lazulis Knight - Andy Buchan
Lazulis Guard - James Barriscale
Citizen - Nigel Pilkington
Sorceress - Maria Darling
Dagran - Nico Lennon