Having been brought down in the penalty box, Cummings saw his spot-kick saved by Kevin Cuthbert, but did enough to force home the rebound.
Rovers enjoyed a strong first half, but faded as the hosts seized control after the interval through Cummings' strike.
Hibs move second in the Championship, three points behind Rangers.
A Jason Cummings goal early in the second half was sufficient to see Hibernian return to winning ways against Raith Rovers.