Manager Clint Hurdle said the left-handed De La Rosa, who struck out seven in six innings to beat the Nationals on Friday night, will start on Thursday night at Dodger Stadium.
Veteran lefty Glendon Rusch will move to the bullpen.
The decision to start De la Rosa -- who is 6-6 with a 6.16 ERA in 16 starts and five relief appearances -- was made with an eye toward next season. De La Rosa, 27, is eligible for arbitration this winter.
"I want to give Jorge every opportunity to show me this is something he can handle," Hurdle said. "I think Jorge has age on his side. There's a more dynamic arm.
"That's not to take anything away from Glendon's efficiency, but right now I think we need to make sure we are creative and proactive looking at this."
Since the All-Star break, De La Rosa is 3-1 with a 4.11 ERA. He has pitched even better than that, as the ERA is inflated by one bad outing, in which he allowed seven earned runs in 1 2/3 innings against the Marlins on July 31.
De La Rosa pitched well against the Nationals on Aug. 5, but he was moved to the bullpen because left-hander Jeff Francis rejoined the rotation and the club acquired Livan Hernandez off waivers from the Twins.
When Aaron Cook had a start delayed because of back trouble, however, De La Rosa made the most of his spot-start on Friday.
For a young pitcher capable of a mid-90s mph fastball and a biting slider, De La Rosa is well-traveled.
He pitched for the Brewers (2004-06) and the Royals (2006-07) before the Rockies acquired him in a trade earlier this year. Before his Major League tours, he pitched in the Diamondbacks' system, the Mexican League and the Red Sox's chain.
Hurdle said the Rockies have heavily coached De La Rosa, and he has responded.
The skipper declined to go into specifics. But pitching coach Bob Apodaca has spent great amounts of time with De La Rosa, and Rockies performance enhancement coach Ronn Svetich, an expert in sports psychology, also has been involved in the process.
"I think it's a good fit for him, and he's growing up," Hurdle said. "I think a vote of confidence right about now may be something that can help him."
Thomas Harding is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.