The striker reacted quickest to a loose ball in the box after comedy defending from the Bees to lash home an angled drive from 12 yards.
It was no more than the visitors deserved after restricting the home side to only a handful of shots on goal throughout the 90 minutes. Brentford’s only real effort came on 52 minutes when Niall McGinn cut in from the left and fired a dipping drive just over.
Rosler’s side started brightly but their dismal home form continued as they failed to trouble goalkeeper Chris Day until the final minute, when Miguel Llera’s header from a McGinn corner was straight at him.
Former Bee John Mousinho might have broke the deadlock just after the hour mark when his sizzling low drive was stopped at the second attempt by keeper Richard Lee.
But the visiting fans had to wait until the 73rd minute for the goal that gave them their first league win over the Bees.