Romero (10-7), who was signed to a five-year extension worth $30.1 million on Saturday, gave up a run on six hits with three walks and four strikeouts for the Blue Jays, who have won three of four. Adam Lind hit a solo home run while Aaron Hill drove in two in the win.
"I had my fastball, curve ball and cutter going good today," said Romero. "I stayed in the strike zone and got groundball outs. It worked out for the best today."
Dan Haren (1-3) was tagged for four runs on nine hits with a walk and five strikeouts over seven innings of work for the Angels, who dropped two of three in the set after sweeping the Royals. Mike Napoli's solo homer accounted for the offense.
"We keep ourselves in the game with our pitching," said Angels manager Mike Scioscia. "We had opportunities, but we couldn't get those big hits to get ourselves back into the game."
The Blue Jays took the lead in the second on Lind's one-out, solo homer to right-center.
In the fourth, Toronto made it a 2-0 lead as Hill's single to right scored Yunel Escobar.
After stranding men on first and second in the fourth, the Angels got a leadoff homer from Napoli in the fifth to make it a 2-1 game.
Toronto, though, got that run back and another one in the sixth. With the bases loaded, Hill hit into a fielder's choice that scored Jose Bautista and Lyle Overbay followed with a sacrifice fly to score Vernon Wells for a 4-1 lead.
With Jason Frasor on the mound to start the eighth, Alberto Callaspo walked to start the inning and Torii Hunter followed with a single. Howie Kendrick, though, hit into a double play and Juan Rivera flied out to end the frame.
Kevin Gregg struck out the side in the ninth for his 27th save of the season.
Romero has won his past three decisions and is 2-2 lifetime against the Angels...Haren fell to 5-2 against Toronto...Despite the loss, the Angels took six of nine from Toronto this season...Toronto starts a three-game set in Oakland on Monday...The Angels begin a three-game series in Boston on Tuesday...After the game, Toronto placed reliever David Purcey on the 15-day disabled list, retroactive to August 12, and recalled left-hander Jesse Carlson from Triple-A Las Vegas.