Carlisle ended a run of six home games without a win in some style.
Although Jose Baxter netted from the spot, the goal came too late to extend Latics' four game unbeaten spell.
Ryan Noble was getting forward well in support of the Carlisle attack and his run led to Garner's goal which broke the deadlock in the 58th minute.
Noble's chipped cross from close to the by-line found Garner unmarked at the far post for a simple header to provide him with the third goal of his loan spell from Watford and Garner was on target again in the 74th minute, darting in to head home Robson's cross from the left at the far post from six yards.
Robson went from provider to scorer in the 82nd minute, banging the ball home left-footed from six yards after Noble had played the ball into his path.
With Latics looking to repair the damage Baxter was unlucky to strike the woodwork and then in the 85th minutethe same player coolly clipped a penalty past wrong-footed Carlisle goalkeeper Mark Gillespie.