Veteran back-up Byron Leftwich will make his first start for the Steelers in place of Roethlisberger, who suffered the injury against the Kansas City Chiefs on Monday night.
Roethlisberger sprained the sternoclavicular joint in his right shoulder after being sacked by Chiefs linebacker Justin Houston during Pittsburgh's 16-13 win.
In relief Leftwich went 7-of-14 for 73 yards and will now be given the chance to play behind centre from the start at Heinz Field.
But the loss of Roethlisberger is a major blow for a team which is trying to topple the Ravens from the top of the division.
A victory will put the Ravens two games ahead of their arch-rivals, with the return clash in Baltimore scheduled for December 2.