However, Roethlisberger is wearing a special boot and may be limited in practice this week because of the injury, suffered in the first half against Buffalo last weekend.
"I am going to be optimistic and hopeful and he may be a full participant, but there is a chance he couldn't be," Tomlin said. "There is some pain and discomfort. We will see where the week takes us."
Roethlisberger threw for 246 yards but was sacked five times in the Steelers' 19-16 overtime victory against the Bills.
After being suspended for the first four games this season, Roethlisberger has completed 62.3 percent of his passes for 1,825 yards with 12 touchdowns and just four interceptions.
Sunday's game will be a key one with the Steelers and Ravens tied with 8-3 records atop the AFC North.