Ian Ross and Tom Cahill came into the starting line up and it was the home team who made the brighter start with Mark Hudson and Derek Holmes linking up to enable Ross to cross but his effort was cut out by the keeper.
Then a Dale Tonge cross saw a Holmes shot blocked before the Bees answered with a corner from which Bennett had a header saved by Andy Warrington.
He then kept out a header from Elder and at the other end Jamie Green crossed for Holmes to have a header saved before a Ross free kick was cleared and then the midfielder fired a 25 yarder over the bar.
The visitors almost took the lead on 19 minutes when Dickson found Brown who saw Warrington pull off a brilliant save to turn the ball out for a corner.
After four Brentford corners the Millers came close to taking a 26th minute lead when good work saw Cahill win a corner. The ball was cleared to the edge of the penalty area where Hudson returned as fine goalbound shot only for Bennett to head off the line with the keeper beaten.
The visitors were to go on and break the deadlock on 39 minutes when a long ball from Dickson was touched on by Brown to leave Elder with time and space to give the keeper no chance.
Almost immediately the Millers could have levelled matter when Green crossed to find Dale Tonge but his header went just wide and in the last minute of the first half Bennett had a shot saved by Warrington.
Early in the second half a free kick was played back into the Brentford area only for Hudson to fire well wide and then a good ruin by the visitors' Smith saw him cross in front of the face of goal.
Substitute Peter Holmes had a shot saved while for the Bees Brown shot well wide and Elder had a header saved before Jamie Green had a shot blocked.
Hudson also saw a shot saved as the Millers battled for an equaliser and after a Peter Holmes free kick had brought no reward it was all square again on 88 minutes when Hudson scored with a dipping shot from the edge of the penalty area.
Derek Holmes then headed wide from a Peter Holmes cross and a corner brought no reward for the home side as the game went deep into stoppage time.
It was in the 93rd minute that the Bees grabbed a winner with a pass from Mousinho finding Connell who had time and space to beat Warrington and snatch all three points to leave the Millers undeservedly empty handed.
Rotherham: Warrington, Joseph, Mills, Coughlan, Green (Taylor 78), Tonge, Ross (P. Holmes 46), Harrison, Hudson, D. Holmes, Cahill (Newsham 57). Subs: Oxley. Haggerty.
Brentford: Brown, O'Connor, Bennett, Smithy, Pead, Poole, Heywood, Dickson, Shakes, Elder, (Connell 84), Shakes (Mousinho 84). Subs: Reid, Osborne, Hamer.
Referee: Neil Swarbrick (Lancashire).
Attendance: 2,979 (119 away).
