Roethlisberger completed 22-of-34 passes for 217 yards as the Steelers (5-6) continued a comeback following a 2-6 start to the season.
Antonion Brown made six grabs for 92 yards with a score and Emmanuel Sanders also hauled in a TD pass.
On defense, the Steelers got a 21-yard interception return for a touchdown from William Gay and forced four turnovers.
The Browns (4-7), meanwhile, dropped a fifth in six games as Jason Campbell was limited to 14-of-22 through the air for 124 yards before leaving in the third quarter with an apparent upper-body injury.
Josh Gordon racked up career-high 237 yards on 14 catches.