They had their captain, Chris Coyne, and Irish midfielder Steve Robinson sent off in the first half, to be joined later by defender Anthony Grant.
It loaded everything in Rovers' favour but, as they failed to break through, they had to settle for hitting the post twice and seeing Luton's Jaroslaw Fojut make a sensational clearing header from under the bar in stoppage time.
Coyne was sent off as early as the 13th minute for bringing down Andy Williams from behind.
That was a straight red. Robinson's dismissal was more involved, a warning word from referee Andy Hall and then two yellow cards within three minutes, the first for shirt-tugging, the second for a foul five yards outside the box.
Coyne's foul had been well inside and Rickie Lambert stepped up confidently to slam the spot-kick into the bottom right-hand corner for Rovers' seventh penalty success of the season.
The big striker could have had a hat-trick before half-time but was twice defied by Dean Brill in Luton's goal, who fended shots for corners.
Luton were taking risks in defence as they tried to pull back the goal and their tactics paid off.
Early in the second half, David Edwards glanced a header from David Bell's free-kick past the crowded defence to level the scores.
Suddenly, it was game on and, even after losing Grant to another straight red card for a foul just outside the box, Luton turned in a stirring performance.
Rovers, who have only won once at home, saw Steve Elliott find the bar from 20 yards before Williams sent in a shot from the right which flew off the keeper's foot on to the far post.