He's expected to make a full recovery by training camp.
Roethlisberger played in all but three games last season, sidelined with shoulder and rib ailments. The 31-year-old passed for 3,265 yards, 26 touchdowns and eight interceptions last season.
"Earlier today, Ben had minor surgery on his right knee that was the result of slight discomfort this offseason," Tomlin said. "We advised him to get the surgery done to ensure he will be completely healthy for the start of training camp. This surgery will have no long-term effects on his health."