Enjoying fine work under a makeshift pitching plan, the Rockies had a 4-2 lead in the sixth. Todd Helton led off with a double off Dodgers starter Chris Capuano (7-2), the squirrel made his frenetic run from the first-base side over to Rich Dauer in the third-base coaching box. Jordan Pacheco grounded out, then Rosario smashed Capuano's first-pitch changeup into the left-field stands.
From there, the home team became a thundering herd.
Chris Nelson, in his first appearance since returning from a wrist injury that kept him off the field since May 15, knocked his first homer of the season in the eighth inning, and Michael Cuddyer followed immediately with his seventh long ball to complete the rout. With three straight games scoring in double figures, the Rockies are feeling less like their 22-29 record and more like a team that will make itself relevant.
"That's the game we need to play," said Rosario, who leads NL rookies with eight homers. "Have fun. I told everyone in the beginning that we were going to be good. We couldn't be bad all year. Something good was going to happen."
The Dodgers had won four of the previous six meetings. But Matt Kemp is out with a hamstring injury. Pitcher Ted Lilly, who dominates the Rockies, is out with left shoulder inflammation, and 2011 NL Cy Young Award winner Clayton Kershaw's turn doesn't come during this three-game series.
The Rockies are missing one of their big guns, with Friday being shortstop Troy Tulowitzki's second day on the 15-day DL with a left groin strain. But they have found plenty of firepower throughout the lineup.
"What can I say that I haven't said the last three games?" Rockies manager Jim Tracy said. "We just continue to swing the bats well."
Helton went 2-for-3 to run his hitting streak to eight games, Carlos Gonzalez went 2-for-4 with an RBI to run his total to 45 and his hit streak to six games (15-for-24, .625) and leadoff man Dexter Fowler had three hits and two RBIs while hitting safely in his sixth straight game.
"This is a great opportunity for us to step forward and beat those guys, try to get wins and move closer to them," Gonzalez said. "If you want to win the division, you have to take every opportunity."
Dodgers third baseman Ivan De Jesus' throwing error let Cuddyer reach to open the second, and Rosario followed with a walk. When catcher Matt Treanor's attempt to cut down Rosario stealing second sailed into the outfield, both runners came around to score for a 2-0 Rockies lead. Pacheco hit into a double play that scored Cuddyer in the fourth and Gonzalez hit an RBI single in the fifth to give Colorado a 4-1 lead.
"We gave them too many outs, too many extra bases tonight," Dodgers manager Don Mattingly said. "You can't do it in this ballpark."
Throughout a four-game sweep of the Astros, Rockies starting pitching -- a problem all season -- did well enough to win games that were hard to lose because of the high scoring. This time, led by a starter trainee, the Rockies pitched well enough to win most any game.
Colorado parted ways with veteran Jamie Moyer this week and moved lefty specialist Josh Outman, who had made 25 starts in 33 appearances with the Athletics the last three years, into the rotation. However, Outman was limited to roughly 50 pitches. He used 55 to hold the Dodgers scoreless for 3 1/3 innings, with two hits, a walk and five strikeouts.
Outman needs to improve his fastball command, which will help his efficiency, but he mixed in an effective changeup -- which he rarely used as a reliever because he faced few right-handed hitters -- and felt good about Friday.
"Tonight was one of those nights where I felt good, had my pitches working and was executing the game plan I had gone over with the pitching coach [Bob Apodaca] and the catcher," Outman said.
Outman struck out the dangerous Andre Ethier to open the fourth before giving way to Carlos Torres, who gave up two runs and three hits in two innings.
Righty reliever Adam Ottavino (1-0), who saw time with the Cardinals in 2010 but wasn't present for the arrival of the famed St. Louis Rally Squirrel during a World Series run in 2011, earned his first Major League win by striking out three and giving up two hits in 1 2/3 innings.
Rosario's power made sure the victory happened.
Castilla christened Rosario with the "Baby Bull" moniker in Spring Training. Rosario, 23, said Friday he had not heard of Hall of Famer Orlando Cepeda, who had the same nickname when he played from 1958-74.
Rosario also is early in his education as a hitter. He can swing wildly at breaking balls out of the zone, but when his discipline is right, he can bull over any pitcher.
"I know I'm a rookie guy," he said. "It doesn't matter to me if I'm behind or close to other people as a hitter. I'm in the lineup and I'm going to enjoy every time I get to hit."