The 26-year-old found first-team football hard to come by last season and was limited to mostly appearing from the bench for the Gunners.
Manager Arsene Wenger signed Gervinho from Lille in 2011 but he was only able to find the back of the net on four occasions in his first campaign at the Emirates Stadium and added seven last term.
A Ligue 1 and Coupe de France double followed in 2011 and he was identified by Wenger as the player to add goals and pace to his frontline.
Gervinho started last season in fantastic form, scoring five goals in the opening seven games before travelling to represent his country at the CAF Africa Cup of Nations.
Roma finished sixth in Serie A last season but have had a busy summer in the transfer market, with Gervinho being the 13th addition to Rudi Garcia's squad.
Announcing his departure on their website, Arsenal said: "Everyone at Arsenal would like to thank Gervinho for his contribution to the club and wish him well for his future career."