Janikowski's decisive boot as time expired came after nine-play, 49-yard drive and handed the Raiders (1-2) their first win under new Coach Dennis Allen.
The Oakland kicker also forged a 31-31 tie with a 32-yard effort with 6:30 left in the fourth quarter.
Carson Palmer gained 209 yards on 23-for-33 passing, connecting on three TD passes with an interception.
Darren McFadden amassed 113 rushing yards with a score on 18 carries for the Raiders.
Pittsburgh (1-2) got 384 yards from Ben Roethlisberger, who went 36-of-49 passing with four touchdowns.
The Steelers' Mike Wallace hauled down eight passes for 123 yards and a touchdown.