Both sides had chances to find the net during the opening 45 minutes at the Stadio Olimpico.
However, young Argentine Lamela was the only player able to break the deadlock. Captain Francesco Totti played in the attacker, who sent the ball beyond the reach of Andrea Consigli in the away goal with 30 minutes played.
The goalkeeper's resistance was eventually broken with 62 minutes on the clock when American midfielder Bradley turned the ball into the net from an acute angle.
Roma continued to dominate the encounter, although they were unable to add to their tally.