Beaten at home against Charlton last time out, Uwe Rosler’s men bounced back with a three-point haul courtesy of Saunders, who collected Mike Grella’s flick-on to shoot home from a tight angle after 79 minutes.
Nicky Adams went close on two occasions for Rochdale in the opening exchanges but the hosts’ bright start paled when they conceded a penalty 11 minutes in.
Stephen Jordan’s push in the back of Bees’ frontman Clayton Donaldson left referee Garry Sutton with no alternative but to award the spot-kick and Gary Alexander duly obliged, hammering the ball down the middle of the net past David Lucas.
The hosts pushed for a leveller, with Dean Holden’s overhead kick going close and Adams’ cross to the near post met by Ashley Grimes’ neat flick, the ball beating Bees’ goalkeeper Richard Lee but running wide of the far post.
Rochdale levelled in the 65th minute when Brian Barry-Murphy’s corner was glanced home by the head of defender Marcus Holness. But the Bees came again and Saunders secured the three points.