Reading went close to ending a dismal run which has seen them fail to win a league game at home since January 27, but dogged Doncaster defence and Sullivan's defiance frustrated them.
Reading piled the pressure on after the break with new boy Grzegorz Rasiak coming on as a second-half substitute and almost scoring with both of his first two touches.
Brendan Rodgers sent Rasiak on as Reading were awarded a corner. It was taken by Brian Howard, one of four players making their home debuts for Reading, and headed powerfully towards goal by Rasiak only for Sullivan to make a fine save.
Moments later, and with only his second touch of the ball, Rasiak sent a powerful drive goalwards, but Sullivan leapt to his left to push the ball away.
"Those saves will get the headlines," said O'Driscoll, "but they were there for him to save. They were all saves you would expect him to make."
Reading manager Brendan Rodgers was more generous with his praise of O'Sullivan saying. "His save from Rasiak's first strike was fantastic."
Rodgers added: "I am pleased with the clean sheet but in the second half I thought we were more likely to win.
"Sean changed his formation three times during the game, starting 4-3-3, changing to a diamond formation and in the second-half going 2-3-3-2.
"Our players had to adapt because you can't just keep running around or else spaces open up.
"The international break was both good and bad for us. We had won 3-1 at Barnsley so wanted to keep that going, but on the other hand the break gave us a chance to bed our new signings in."
O'Driscoll said: "We played Reading twice last season and got nothing out of them, so to play below our best and get a point was a plus.
"Reading play a counter-attacking system and we countered that but we couldn't get our own passing game going.
"A few of the boys were going down with cramp at the end. The pitch was hard, a bit like ours, and it was very hot.
"At the end I thought it might come down to a free kick or a corner and we are not set up very well for them."
In the final quarter of the game Reading won a succession of corners and threatened to overwhelm Doncaster but the Yorkshire side held firm.