Roethlisberger was able to practice Wednesday and Thursday, the team said. After Thursday's workout Tomlin said Roethlisberger was returning to the starting position.
"He's been above the line in all areas," Tomlin said of Roethlisberger. "Really, the only question we can't answer is taking a hit. Obviously that will be answered in the stadium on Sunday."
The Steelers play the San Diego Chargers in Pittsburgh Sunday.
Roethlisberger suffered rib and shoulder injuries against Kansas City on Week 10. That started a quarterback carousel for the Steelers. Byron Leftwich replaced Roethlisberger that game and again the following week but was injured.
Charlie Batch, a 15-year pro was inserted in the lineup and delivered an emotional win at Baltimore last week.
The Steelers (7-5) were 1-2 in the games Roethlisberger missed.
Roethlisberger has completed 209-of-316 passes for 2,287 yards, 17 touchdowns and four interceptions this season.