DeRosa connected for a three-run blast and Cabrera added a solo shot during a four-run fifth inning, while Cabrera also provided a run-scoring single as the Blue Jays banged out 15 hits.
Munenori Kawasaki drove in a pair of runs and Maicer Izturis went 3-for-4 with an RBI for Toronto.
Brandon Morrow (1-2) earned his first victory of the season in his seventh start, yielding two runs on three hits over eight innings. The right-hander overcame five walks while striking out eight.
The Blue Jays snapped a four-game losing streak with the triumph in the last of a three-game series.
Mariners starter Joe Saunders (2-4) was roughed up for seven runs on nine hits over five full frames.
Kyle Seager and Robert Andino each drove in a run for Seattle.