DENVER -- Aaron Cook was ready to take his turn in Colorado's surging starting rotation.
Cook (3-3) allowed two runs and six hits. He walked two and struck out two, improving to 2-0 in three career starts against the Astros.
"We are a competitive group and after seeing what Byung-Hyun Kim did on Friday and what Jason Jennings did last night," Cook said, "I wanted to keep it rolling and keep the competitive spirit alive."
Kim struck out nine in seven innings and kept the Rockies in position to win Friday with a ninth-inning rally. Jennings tossed the second shutout of his career on Saturday.
"It can very well be contagious," Colorado manager Clint Hurdle said. "There is a spirit of competition where the momentum of one guy's start is turned into the momentum of your own."
Cook attempted to get Colorado's second consecutive complete game but Morgan Ensberg led off the ninth with a single and Jason Lane walked to chase the right-hander from the mound. Brian Fuentes got Brad Ausmus to hit into a double play before Adam Everett hit an RBI triple and Eric Bruntlett added a run-scoring single to cut the lead to 5-3.
Fuentes then struck out pinch-hitter Craig Biggio with Bruntlett on first to finish his seventh save in eight chances.
It was Colorado's first series sweep at home this season and its third overall. The Rockies (19-13) also improved to six games over .500 for the first time since Sept. 14, 2000, when they were 76-70.
Helton was 1-for-3 with a walk and his first home run since coming off the disabled list on Friday. Cory Sullivan had two hits and an RBI for the Rockies.
Houston starter Fernando Nieve (1-1) allowed five runs and nine hits in 5 1/3 innings.
Lane hit a solo home run for the Astros, who were swept by the Rockies for the fifth time, all in Denver. The last time was May 29-31, 2000. Everett finished with three hits.
"We didn't play very well this weekend," Houston manager Phil Garner said. "I thought we gave up a couple of ballgames. We didn't play very inspiring baseball."
Colorado tied it at 1 in the fourth inning on a one-out double by Matt Holliday, a walk to Brad Hawpe and Clint Barmes' bloop double to right. Nieve retired Danny Ardoin and Cook to get out of the inning.
The first four Rockies reached against Nieve in the fifth as Colorado extended its lead to 4-1. Helton followed a double by Sullivan and an infield single by Jamey Carroll with a three-run homer into the Colorado bullpen in right. Garret Atkins doubled before Nieves retired the next three batters.
"I hit a hanging changeup," Helton said. "I was trying to get the ball up into the air and out of the ballpark."
"I was behind in the count and just trying to throw a changeup for a strike," Nieve said. "I left it up there and he got it real good."
The Rockies added a run in the sixth when Ardoin doubled, moved to third on a groundout and scored on Sullivan's sacrifice fly.
Discomfort in the right shoulder of RHP Mike DeJean (right shoulder tendinitis) will force the Rockies to shut him down for the next five days. ... Biggio and OF Preston Wilson were out of Houston's starting lineup. ... The Astros placed OF Chris Burke on the DL with an injured left shoulder. They filled his roster spot by purchasing the contract of IF Joe McEwing from Triple-A Round Rock.