Screen Gems is back in good form with thriller The Roommate, which easily beat Universal/Relativity’s 3D Sanctum at the Friday box office in grossing an estimated $6.4 million from 2,534 screens. Sanctum, executive produced by James Cameron, grossed an estimated $3.6 million from 2,787 runs, including more than 2,000 3D runs. The Australian adventure-thriller also is playing in 178 Imax theaters.