Gills took an early lead through Lewis Montrose before Kedwell scored his first from the spot deep in first-half injury time.
Rovers reduced the deficit via Mustapha Carayol but Danny Jackman’s drive and Kedwell’s second penalty put the result to bed against a Pirates side who saw substitute Cian Bolger sent off.
After Frank Nouble had gone close for the hosts, Jackman’s fine left-wing cross was headed in by Montrose after eight minutes. Joe Anyinsah, who had a penalty appeal of his own turned down, then felled Garry Richards in the area and Kedwell made no mistake from the spot.
The away side pulled a goal back after 51 minutes when Carayol danced his way into the Gills area to poke home but Jackman restored the home side’s two-goal cushion with a 20-yard drive.
And Gills put the result beyond doubt after 72 minutes when Bolger saw red for fouling Curtis Weston in the box, leaving Kedwell to thump home the resulting penalty.