“ Tron: Ares ,” the latest entry in a five-decade old franchise that’s more of a cult favorite than a commercial juggernaut, debuted to a solid $4.8 million in Thursday previews. The sci-fi sequel is expected to open to roughly $45 million from 4,000 North American theaters over the weekend, easily topping new releases such as Paramount’s R-rated dramedy “ Roofman ,” starring Channing Tatum and Kirsten Dunst, and “Kiss of the Spider Woman,” a musical with Jennifer Lopez as a fantasy film queen.