Matt Ritchie gave the hosts the lead in the eighth minute only for midfielder Danny Hollands' to put through his own net two minutes later.
Doncaster were twice rescued by the woodwork before the half-time whistle and an honest Saunders admitted: "We got battered at times. But we dug in to get a draw when we were nowhere near our best.
"Swindon got lots and lots of balls into our box but we defended well and our goalkeeper had the most to do all season, and the woodwork helped us as well.
"We are still second and a point away at Swindon is good. Swindon will be in the top six at the end of the season but the main thing is they didn't beat us.
"Swindon were favourites to go up before the season started and we wasted opportunities early in the game as a few of us struggled, but we pulled through."
Home manager Paolo Di Canio was frustrated his injury depleted side did not come away with all three points and close the gap on second-placed Rovers.
Di Canio, who had 11 senior players on the sidelines, said: "I am disappointed because we deserved the three points. We have to keep the ball and we practice this. We we practice more than other teams in the league, but there is a limit to improve the individual.
"We have to be happy with the way we wear the shirt because we need pride and dignity, and we will win a few games. I didn't check the table but before there were five points between us and 12th place, now maybe two, so if we dominate but don't win we will drop.
"Nobody can be angry, my fans or myself, because if you play like this and dominate we will score if we don't concede an own-goal, and 90 per cent of the time we win the game."