Rovers dominated a one-sided South Yorkshire derby clash, but the Blades hit back with two goals in the last 10 minutes after Doncaster had striker Billy Paynter sent off.
Paynter had given Rovers the lead from the penalty spot in the 18th minute after visiting goalkeeper George Long had brought down David Syers, who made it 2-0 with a 63rd-minute header from David Cotterill's free-kick.
Doncaster looked to be well in control until the visitors pulled one back with a controversial penalty award converted by Nick Blackman after Joe Ironside had been judged to have been brought down by Andy Griffin in the 80th minute.
Paynter was sent off seven minutes later after tangling with Blades defender Tony McMahon and Dave Kitson grabbed the equaliser in stoppage time.
Saunders said: "We played really well and could have scored seven or eight goals, but the referee's decisions have done us at the end of the day.
"I thought their keeper should have been sent off for the blatant foul which gave us our penalty and it should never have been a sending off for Billy Paynter. I've seen it again on the video and he did not do anything, it was just a tangle of legs.
"Then they've been given a penalty when their lad has had hold of Andy Griffin's shirt. I'm fortunate to have had the benefit of seeing it again, but the ball was running away from Ironside and the lad just went down.
"I'm finding it difficult to speak because what's happened is hard to swallow.
"The referee's decisions have cost us two points. I'm sick we've not got over the line and won the game after playing so well, but we just have to put it behind us and get on with it."