Coach Mike Tomlin said Tuesday that Roethlisberger is "day-to-day" but is working "tirelessly" to be on the field against the 49ers.
Roethlisberger left last Thursday's 14-3 win over Cleveland in the second quarter after turning the ankle while getting sacked. He returned to throw for 178 yards and a touchdown in the second half.
Neither Roethlisberger nor center Maurkice Pouncey, who is also dealing with a sprained left ankle, practiced on Monday.
Tomlin says Roethlisberger will have to practice at some point this week if he intends to play, adding he believes the extra day of rest will almost certainly benefit the quarterback.