Roethlisberger racked up 214 yards and both of his scoring tosses went to Antonio Brown, who reached the end zone on 77- and 44-yard receptions and finished with four catches for 137 yards.
The Steelers also got a defensive touchdown from Crezdon Butler, who returned an interception 95 yards.
The victory was tempered by the losses of reserve quarterback Byron Leftwich and starting center Maurkice Pouncey, both of whom left the game with injuries.
Atlanta's Matt Ryan hooked up on 22-of-42 passes for 220 yards, a touchdown and an interception, while back-up Chris Redman connected on 8-of-18 passes for 89 yards and a pick-off.
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