Goals from Macaulay Gillesphey and Joseph Champness had Roar two goals ahead, and a straight red card for Marco Urena just after the hour preceded more Mariners woe with subs Alex Parsons and Masato Kudo on target late on at Central Coast Stadium.
A third straight win sees Roar up to seventh, just one point shy of sixth-place Western United, while the Mariners are still third but now have just one win in their past eight.
Victory also means Roar are undefeated in 19 games against the Mariners (W15, D4), marking the longest undefeated streak of any team against a single opponent in A-League history.
The breakthrough arrived after 19 minutes when Gillesphey volleyed home at the back post after Jay O'Shea's right-wing cross was deflected into his path.
Champness brilliantly drilled home a 25-yard effort for his first A-League goal in two years shortly before Urena saw red after a VAR check for a poor tackle on O'Shea.
Parsons bent home his first A-League goal in the 89th minute and the scoring was completed with a near-post finish by Kudo in injury time.