The Athletics raised their record to 5-2 to start the season. The Angels have just two wins in seven games.
One of Rosales' RBIs was a solo homer. Ryan Sweeney put in a 2-for-4 performance with an RBI and Dallas Braden (1-0) earned the victory after holding the Angels to three runs on five hits over six innings.
Tyson Ross hurled three innings of one-run relief to get his first career save.
Los Angeles got solo homers from Bobby Abreu and Juan Rivera. Joe Saunders (0-2) was tagged for four runs on four hits in six-plus innings.