Roberts had walked, stole second and scored on a single by Miguel Tejada before coming out of the game, which the Orioles lost, 7-6.
Manager Dave Trembley said Roberts suffered the injury while stealing second base, probably by hitting the corner of the base in his headfirst slide.
"It's a devastating thing, losing your leadoff guy who comes out and sets the table," Trembley said.
The Orioles' leadoff hitter, Roberts was starting in his fourth straight game despite being slowed this spring with a herniated disc in his lower back. He snapped an 0-for-10 skid with two hits on Thursday night, picking up his first stolen base in the Orioles' 5-4 win against the Tampa Bay Rays.
Utility man Julio Lugo replaced Roberts at second base and went 0-for-4.
Brittany Ghiroli is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.