Hundley's blast in the sixth inning put the Padres ahead 4-1 and he added a run-scoring single in the next frame, finishing with three RBI in the victory.
Ross (1-4) snapped a personal 12-game losing streak dating back to last year, controlling Milwaukee one run over six innings. He allowed just two hits, walked two and struck out six.
Donovan Hand (0-2) was tagged with the loss, allowing a pair of runs on seven hits over four innings.
Khris Davis, called up Monday from Class AAA Nashville to replace the suspended Ryan Braun, socked his first major league homer for the Brewers.