The Giants moved within a game of the Rockies for the lead in the National League wild-card race. Colorado had a four-game winning streak halted.
The Giants had a 3-1 lead in the fourth when Rowand came through with his key blast, his 11th of the season.
Sanchez (6-10) gave up just two hits and one unearned run. Four San Francisco relievers combined to surrender two runs on seven hits the rest of the way.
Brian Wilson struggled to finish off the game in a non-save situation, giving up three singles and a run in the ninth. He struck out Omar Quintanilla, the potential tying run, to end the game.