Roethlisberger's 5-yard TD toss to Mewelde Moore in the first quarter put the Steelers ahead to stay at 7-0, and his 7-yard scoring strike to Antonio Brown in the second extended their lead to 17-7.
The Steelers' signal-caller finished 36-of-50 passing with one interception.
Shaun Suisham booted three field goals as Pittsburgh (6-2) recorded its fourth straight win.
Heath Miller made seven grabs for 85 yards for the Steelers, who beat New England for only the second time in seven meetings at Heinz Field.
The Patriots' Tom Brady was held to 198 yards on 24-of-35 passing efficiency, although he did connect with Deion Branch and Aaron Hernandez on touchdown passes.
New England (5-2) was limited to 43 rushing yards.