Brett Harris added a two-run double for Oakland, which had lost seven of its previous eight games and 17 of 21.
Nolan Schanuel had two hits and four RBIs for the Angels, who had won six of their previous seven games.
Butler and Rooker homered off Angels starter José Soriano in a four-run fourth inning.
“It’s obviously great to see the young guys … produce. It’s been a while since we’ve hit a three-run homer, so that’s always nice,” manager Mark Kotsay said.
Rooker’s 16th homer came on an 0-and-2 knuckle curve Soriano left over the plate. Butler’s opposite-field shot barely grazed the left-field foul pole.
Kotsay attributed a mechanical adjustment to Butler’s home run.
“It’s going to process for him to be able to duplicate it, but that swing he took on the three-run homer, shorter, less head movement, more direct to the baseball, and thus the result happened,” he said.
Harris’ two-run double in the sixth highlighted a three-run inning in which Oakland extended its lead to 7-1.
The Angels closed to within 7-3 in the seventh on Schanuel’s two-run single.
Schanuel doubled in a run off A’s closer Mason Miller, who gave up two runs in the ninth in a non-save situation.
Spence (5-4) gave up one run and six hits to end a streak of five straight winless starts. He struck out five and did not give up a walk. He has walked no more than one in seven straight starts.
Soriano (4-6) gave up four runs and three hits in four innings. The hard-throwing right-hander was activated from the injured list earlier in the day after sitting out three weeks because of an abdominal infection. He was on a 65-pitch limit.
Soriano’s effort coming back from the injury was an encouraging sign for the Angels, manager Ron Washington said, noting Soriano would likely see his pitch limit bumped up to 85 in his next start.
“He’s back,” Washington said. “We’ll see where it goes from here, but I was pleased with the way he threw the ball. You always wish you don’t give up any runs, but it happens.
“I thought he handled himself very well out there.”
Before the game, the Angels put right-hander Andrew Wantz on the 15-day IL because of right elbow inflammation.