Bologna pulls off stunning Roma win
The Giallorossi looked to be cruising when Alessandro Florenzi and Erik Lamella struck in the first 15 minutes, but two goals in as many second-half minutes from Alberto Gilardino and Alessandro Diamanti brought Bologna back on level terms.
And there was one final twist in the dying seconds when Gilardino grabbed his second of the match after an embarrassing mix-up in the Roma defence.
Roma had gone into the match unbeaten in the league and got off to the best possible start with a goal after six minutes from Florenzi, who headed home the rebound after Francesco Totti had hit the post from 35 yards.
Diamanti saw his attempt at an equaliser saved by goalkeeper Maarten Stekelenburg and the home side took advantage by adding a second on the quarter hour with an unstoppable right-footed shot from Lamela.
Roma had the ball in the back of the net for a third time after 32 minutes but Mattia Destro was deemed to be offside when he hit his shot from inside the box.
Totti also went close with a lob which skimmed the crossbar as the interval approached.
Roma continued to rule the roost at the start of the second half and visiting goalkeeper Federico Agliardi did well to turn away a cross-shot from Totti.
Stekelenburg was also on his guard at the other end when punching away a drilled effort from Gilardino.
And the momentum began to swing Bologna's way when they scored twice in two minutes.
Gilardino grabbed the first after 72 minutes, heading home a cross from Nico Pulzetti, and the striker turned provider moments later for Diamanti to tuck the ball into the bottom right corner.
Roma struggled to recover from the double blow and they were hit by a final sucker punch in the dying seconds when Stekelenburg collided with team-mate Nicolas Burdisso allowing Gilardino to cap a remarkable second-half display with an easy tap-in.