Ortiz connected off Mike Koplove to snap a 3-3 deadlock after Arizona scored a run in the top of the eighth to tie it. The blast made a winner of Mike James, while Kent Mercker worked a scoreless ninth for the save.
Rockies starter Shawn Chacon pitched seven strong innings, allowing two runs and seven hits with two walks and three strikeouts.
Mike Morgan got the start for Arizona and gave up one run and three hits in four innings. But all three Diamondbacks relievers gave up a run.
Pinch hitter Kevan Burns homered for Arizona, which sent most of its regulars to Las Vegas for a night game against the Los Angeles Dodgers.