Ross (2-4), recently promoted to San Diego's starting rotation from the bullpen, was scintillating in a second straight start after yielding just one run in six innings Tuesday against Milwaukee.
The right-hander allowed just three hits and one walk while striking out seven for the Padres, who took the rubber match of a three-game series.
Huston Street tossed a 1-2-3 ninth for his 19th save.
San Diego notched the game's only run on Carlos Quentin's RBI single in the first.
Arizona's Patrick Corbin (12-2) was hung with the hard-luck loss, yielding just the one run on six hits in an eight-inning effort. The Diamondbacks ace didn't issue a walk and fanned eight.
The second-place D-backs came into contest trailing the National League West-leading Los Angeles Dodgers by 1 1/2 games.