Ryan finished 18-of-36 passing for 205 yards and two touchdowns, rallying the Falcons (10-2) from a 10-point, fourth-quarter deficit to their sixth straight win.
Michael Turner rushed for 88 yards and a touchdown on 24 carries, helping Atlanta maintain its one-game lead over New Orleans in the NFC South and in the overall NFC standings.
The Falcons haven't lost since an Oct. 17 defeat at Philadelphia.
Tampa Bay quarterback Josh Freeman threw for 181 yards and a touchdown but was picked off by Atlanta cornerback Brent Grimes late in the game to snuff out a potential go-ahead drive.
The Buccaneers dropped to 7-5 with the setback.