I'm not so sure that's official; it just says:
EVERYONE! SPAM THIS LINEUP ON THE OFFICIAL RockstarUPROAR PAGE!!!
UPROAR FESTIVAL 2012
ALL THAT REMAINS
Battle of the Bands Winner
Anyway, Papa Roach, Shinedown, Staind and FFDP are good choices. I still think Uproar won't be complete until they have a run with Alter Bridge, Mudvayne, Drowning Pool and Godsmack.