He took over for faltering starter Chad Bettis and pitched four perfect innings as the Rockies defeated the Pittsburgh Pirates 11-5.
The Pirates had won eight straight games at Coors Field, a streak that De La Rosa was instrumental in ending.
He made his 65th major league relief appearance, and the four innings are his longest stint out of the bullpen. Only one of the 12 batters he faced hit a ball to the outfield as De La Rosa struck out five and threw 31 of 47 pitches for strikes.
De La Rosa (2-4) was the Rockies' Opening Day starter but was demoted to the bullpen after going 1-4 with an 11.41 ERA in six outings. He pitched two innings in each of his first two relief appearances and eight days after he last pitched, De La Rosa came to Bettis' rescue after he squandered nearly all of a five-run lead in the fourth.
Rockies manager Walt Weiss said of De La Rosa, "The curveball is back in play. He's got a lot of confidence in it, and it was a real big pitch for him today. He used his fastball more. These are things we talked about after we took him out of the rotation, and he's embraced it."
Pirates starter Jeff Locke (5-4) pitched six scoreless innings and won here on April 25. And Locke had won four straight starts for the first time in his career. But he was in trouble from the start as the Rockies pounced on him for four straight hits to open a four-run first and scored two more in each of the second and fourth before driving him from the game after 4 2/3 innings in a three-run fifth.
"I didn't do a very good job locating pitches," said Locke, who allowed 11 hits and 11 runs. "We threw strikes, and they hit them. We threw balls, and they put the bat on them. Just one mistake led to another one and they capitalized."
DJ LeMahieu drove in three runs with a double and home run and scored three runs. Nolan Arenado had three hits and two RBIs, and Charlie Blackmon and Ryan Raburn each drove in two runs. De La Rosa's bases-loaded sacrifice netted the first run in the fifth, and Blackmon got out in front of a changeup but managed to float a two-run, two-out single into right-center that made it 11-5 and finished Locke.
LeMahieu hit a two-run homer in the fourth, giving the Rockies an 8-5 edge. He doubled home a run in the first. Raburn tripled home two and scored on a ground out.
Arenado's two-run double with two outs in the second put the Rockies ahead 6-1. Bettis, though, gave most of that lead back as he continued to struggle.
"My command was off," Bettis said.
Weiss said, "I don't want to take a starter out after three innings with a lead, especially a guy like Chad who competes as well as anybody. I trusted my eyes; he just didn't look right to me."
Bettis allowed five runs (four earned) and seven hits in three innings. It was the third time in four starts Bettis has failed to pitch five innings, and in that stretch, he is 0-3 with an 11.57 ERA while yielding 32 hits, including six homers.
Bettis gave up an unearned run in the first after shortstop Trevor Story made a low throw on what could have been a double play ball hit by Gregory Polanco. The error moved him to second, and Starling Marte singled him home.
Bettis surrendered a three-run homer to David Freese in the third after yielding a leadoff single and hitting a batter. Josh Harrison followed Freese's fifth homer with a double and scored on Chris Stewart's two-out single that trimmed the Rockies' lead to 6-5.
De La Rosa came on in the fourth to shut down the Pirates and help the Rockies win for the fourth time in five games. De La Rosa, who left the clubhouse before the media entered, is the Rockies' all-time leader with 80 wins. Weiss said the plan all along was for De La Rosa to work his back to the rotation, and that will be discussed.
"He looks like himself again," Weiss said. "He's done a really nice job. Tough pill to swallow for a guy that's been the best pitcher in franchise history, really. But he's handled it well and went back to the drawing board. He's in a good place."
NOTES: The game was a makeup of a rained-out game originally scheduled April 28. ... Pirates RHP Jameson Taillon was optioned to Triple-A Indianapolis after making his major league debut on Wednesday night and LHP Kyle Lobstein was recalled from Indianapolis and pitched 2 1/3 scoreless innings as he began his third stint this season with the Pirates ... Rockies C Tony Wolters (concussion) is scheduled to catch nine innings Friday and six innings Saturday in rehab games with Triple-A Albuquerque ... Rockies RF Carlos Gonzalez did not play. Wednesday, he became the first player in franchise history to strike out four times in consecutive games...Rockies RHP Christian Bergman (strained left oblique) is scheduled to throw his first full-go bullpen Saturday since he was injured May 19.