Roma confirmed the deal with a statement that read: "AS Roma can confirm that Adem Ljajic has been sold to Torino FC on a permanent deal for a fee of €8.5m.
"The total sum could eventually rise to €9m, should both player and club meet agreed performance clauses".
Ljajic made a total of 74 appearances for former club Roma, scoring 15 goals.
The 24-year-old has also represented his country on 20 occasions, scoring 3 goals.