The Italian sprinter has shown some excellent for this season and but could only shout out in anger after crossing the finish line behind winner Alejandro Valverde (Movistar) and Davide Appollonio (Ag2r-La Mondiale), who won the bunch sprint, one second behind the Spaniard.
"It's always nice to get on the podium but I've never won as a professional, but I hope it happens soon. I can't believe I went so close today," he told journalists at the finish after the podium ceremony.
"The team did an incredible job and I really wanted to pay them back with a big win but I made a mistake in the sprint. I hesitated a second before launching my sprint and then I was caught between [Philippe] Gilbert and the barriers. I'm not cold-blooded like some of the other sprinters."
With no race radio allowed in Roma Maxima because it is not a WorldTour category race, Colbrelli did not know that Valverde and Pozzovivo had managed to hold off the peloton all the way to Rome. In the closing kilometres, he thought he was about to sprint for victory.
In a hectic and thrilling finale, the sprinters and their teams caught Pozzovivo but Valverde cleverly started his sprint early and crossed the line first.
"To be honest I didn’t know that Valverde and Pozzovivo were away, I only saw then in the finish straight," he said.
"I'd seen that the Yellow Fluo rider (Rabottini) was off the front in the final kilometres but then when we caught him, I thought we were sprinting for the win."
Colbrelli has been riding well since the start of the season and third at Roma Maxima was his tenth top-ten result of the year. He was fourth at the Trofeo Laigueglia and second at last weekend's GP di Lugano.
He is hoping to finally break his duck and win his first ever professional race sometime in March.
"Third is good result and boosts my morale for the sprints," he said.
"I can only hope to win big at Tirreno-Adriatico. This gives me more confidence for Milan-San Remo, too."