Romero (1-0) allowed three hits and two walks in 8 1/3 innings while Lester (0-1) gave up three hits and two walks in eight innings. Romero struck out five and Lester six.
Romero's walks were to the first two Boston batters in the ninth inning and Sergio Santos came on to get the final two outs and his first save.
Romero got the first six batters his faced out and also had a string of 17 consecutive batters retired. Lester had 1-2-3 innings in the first and second and retired 15 in a row in one stretch. The efficient pitching allowed the game to be completed in 2 hours, 13 minutes.
Cody Ross and Mike Aviles opened the Boston third inning with singles and, after a fielder's choice, Jacoby Ellsbury singled, knocking in Aviles. The Red Sox didn't have another base runner until a walk to Ellsbury to open the ninth.
Eric Thames singled to open the Toronto third and, after a strike out, scored on a triple from Rajai Davis. Davis made the score 2-1 on Yunel Escobar's sacrifice fly.
The Blue Jays added a run in the eighth when Davis walked and stole second ahead of an RBI single by Escobar.