Blackmon's homers were among five hit by the Rockies. Three of them -- Nolan Arenado's first-inning solo shot, Wilin Rosario's three-run job later in the first and Blackmon's leadoff tally in the second -- came against Giants pitcher Ryan Vogelsong, who was pounded for five runs and six hits in 1 1/3 innings.
"It's really great when we're clicking as a team and everybody's hitting the ball hard up and down the order," said Blackmon, whose four homers from the leadoff position are one fewer than the Major League-leading five by the Brewers' Carlos Gomez. "It's just that feeling of, 'We're going to get 'em.'"
Corey Dickerson added a two-run shot in the third off reliever Yusmeiro Petit. Blackmon homered again in the eighth off Juan Gutierrez. It all made a winner, for the first time this season, of Opening Night starter Jorge De La Rosa (1-3), who danced with danger, throwing 102 pitches, while holding the Giants to one run in five innings.
Through four games of the current six-game homestand, the Rockies (11-10) have outscored the opposition 32-14. The only loss was Sunday's 10-9 slugfest against the Phillies, and the Rockies have won four of their last five. The Giants have dropped seven of their last 12.
The blowout victory was big for the Rockies, who dropped two of three on an earlier trip to San Francisco, with all the games decided by one run. It came on the day that Michael Cuddyer, the defending National League batting champ, was placed on the 15-day disabled list with a left hamstring strain. Also, No. 3 hitter Carlos Gonzalez, battling left knee tendinitis, was the only starting position player not to reach (0-for-4) and cleanup hitter Troy Tulowitzki's contribution was two walks.
"The middle of the order didn't do all the damage," Rockies manager Walt Weiss said. "It was guys up and down the lineup. That's what we've got to be able to do. We can't count on 'CarGo' and 'Tulo' to do all the damage."
Arenado, who moved to Cuddyer's No. 2 spot in the order, knocked his third homer of the season in the bottom of the first. Tulowitzki walked with two out and Justin Morneau celebrated his National League Player of the Week honor from earlier in the day with a double before Rosario lined his third homer of the year into the left-field bleachers for a 4-0 lead. Rosario has three homers in 12 at-bats against Vogelsong.
Blackmon led off the second against Vogelsong with a second-deck shot to right.
"I'm definitely not happy about it," said Vogelsong, whose only shorter appearance in his career was Sept. 24, 2004, with the Pirates, when he didn't retire a Reds batter. "It's embarrassing, really."
Dickerson, starting in center because of Cuddyer's injury (Blackmon moved to Cuddyer's spot in right), followed a Rosario single in the third by homering to the deepest reaches of center field off Petit.
"It's awesome, especially with Cuddy going down, for the guys off the bench to step up, and I always feel confident in my ability to be able to hit," Dickerson said.
The Rockies could've used more length from De La Rosa after seeing their bullpen take a pounding in Sunday's 4 hours and 7 minutes of offensive merriment.
But after the start De La Rosa endured -- the first three starts lasting just 4 1/3 innings, and the last one a hard-luck loss at San Diego -- a first "W" from the Opening Night starter was acceptable no matter the pitch count.
"I threw a lot of pitches in five innings -- too many," De La Rosa said. "But I mixed a lot of pitches. That's the key."
De La Rosa induced a double play from Buster Posey with the bases loaded and one out in the third, then fanned Michael Morse, worked a double play from Brandon Hicks in the fourth and fanned Morse with two out and two on in the fifth.
"He pitched into some trouble but pitched out of it, which is a good sign," Weiss said. "Pitching out of jams, that's what he's struggled with early on. Last year [when he was 16-8] he was so good at it."
De La Rosa and Rosario had discord on the mound once in Spring Training and on Opening Night, and Jordan Pacheco caught De La Rosa's next three games. Weiss insisted he wasn't separating De La Rosa ad Rosario; the schedule happened to fall that way. Pitching coach Jim Wright has been counseling De La Rosa about a tendency to overthrow, not the catcher's identity.
But any pitcher could use Rosario's power. He is the only catcher in club history with two seasons of 20-plus homers (28 in 2012, 21 last season).
Rosario also visited the mound with the bases loaded in the third for strategy and reassurance, and saw his pitcher minimize damage.
"It's a big moment for him," Rosario said. "He's got really good stuff and he competed."
Righty reliever Tommy Kahnle served as bullpen-saver by striking out five in two hitless innings. It was the sixth time in club history a reliever had fanned that many in a two-inning span.
The Giants' frustration bubbled in the seventh, when Angel Pagan earned an ejection for arguing a called third strike with plate umpire John Tumpane.