Riley Adams homered and scored three times for the Nationals, who have won three straight for the first time this season.
Robles singled his first two times up. After Colorado rallied within 8-7 in the top of the fourth, he answered in the bottom half with his first homer of the season, a three-run drive.
Robles, who was hit by a pitch in the sixth and popped out in the eighth, raised his average from .228 to .248 after beginning the season 0 for 18.
“I believe in myself and in the work I've put in,” Robles said through an interpreter. “I know the results will be there eventually and I've just got to keep grinding.”
The 25-year-old outfielder was Washington's top prospect from 2017-19. He played in 155 games for the 2019 World Series champions, hitting .255 with 17 homers, 65 RBI and 28 stolen bases. Last season, however, Robles hit .203 in 107 games and spent the final month of the season with Triple-A Rochester.
“I truly believe in him and so does this organization," manager Dave Martinez said. “He's got unbelievable skills and we just got to try and get it out of him and we're gonna stick with him. As I've said before, there's gonna be days where I'll give him a little breather but we want him to be our everyday centerfielder.”
C.J. Cron had two hits including his 13th home run and Charlie Blackmon had three hits for the Rockies, who have lost three straight and 14 of 18. Brendan Rodgers extended his hitting streak to 14 games with an infield single.
Washington relievers tossed 5 1/3 scoreless innings and Erasmo Ramirez (1-0) pitched two innings to earn the win. Starter Aaron Sanchez was lifted after giving up seven runs on eight hits in 3 2/3 innings.
Colorado starter Austin Gomber (2-5) retired just four batters, allowing eight runs on seven hits and three walks.
After Cron gave the Rockies a quick 3-0 lead with his homer in the first, the Nationals came back with two-run singles from Nelson Cruz and Robles in their half, and Robles’ RBI single capped a three-run second.
Nationals OF Juan Soto hit his 100th career double. He joined Ted Williams, Mel Ott and Mickey Mantle as the only players in MLB history to reach 100 doubles, 100 home runs, 300 RBI, 400 walks and 500 hits at age 23 or younger.
Colorado collected 12 hits in the loss and now has 20 games this season where the offense produced 10 or more hits, the most in the majors.
ROCKIES: RHP Antonio Senzatela (lower back strain) made his first rehab start for Triple-A Albuquerque on Friday and allowed four runs on eight hits in four innings. He threw 77 pitches and walked one with no strikeouts.
NATIONALS: INF Carter Kieboom (ulnar collateral ligament sprain and flexor mass strain in his throwing elbow) underwent Tommy John surgery on Friday. Manager Dave Martinez said the surgery went well and Kieboom should be ready for spring training. … RHP Aníbal Sánchez (cervical nerve impingement) is playing catch up to 100 feet and could begin throwing bullpen sessions in the next week.
Rockies: RHP Chad Kuhl (3-2, 3.67 ERA) will pitch the second game of the doubleheader. He is 0-2 with an 8.25 ERA in his last three starts. Kuhl is 1-2 with a 5.74 ERA in four career games — three starts — against the Nationals.
Nationals: RHP Joan Adon (1-8, 6.97 ERA) is 0-6 with a 7.62 ERA over his last six starts. He faces the Rockies for the first time.