Kevin Doyle's 76th-minute header from substitute James Harper's free-kick gave the Royals a 2-1 win which was also their seventh straight victory in front of their own fans.
It was also the Republic of Ireland striker's ninth goal this season, all of them coming at the Madejski Stadium.
The goal was needed too as Doncaster had threatened to come away with a deserved point thanks to Jos van Nieuwstadt's header in the 74th minute.
It was the Dutchman's first start since joining Rovers in the summer and he powered home a Martin Woods cross.
All three goals were headers, with Reading defender Andre Bikey having put Reading in front in the 18th minute from a Stephen Hunt free-kick after Rovers had made the brighter start.
Rovers also thought they should have had a penalty with the score at 1-0 when Lewis Guy appeared to have been impeded by Ivar Ingimarsson.
Coppell admitted the expectation had been there for his players to turn on the style following recent thrashings of Sheffield Wednesday and Crystal Palace.
He said: "It never works out that way.
"In the second half we made it very difficult for ourselves although their goal came from a free-kick that wasn't; Stephen Hunt's challenge was perfect. It was the kind of challenge you show young kids how to tackle properly.
"I felt we had more than enough chances in open play to have done significantly better. The game really was tight and credit to Doncaster, they made it very difficult for us."
Doncaster have now managed just one draw in their last eight games but manager Sean O'Driscoll was upbeat about the performance.
He said: "I thought we competed well against a team that, at home, has been a formidable outfit.
"They have scored a lot of goals here and put a lot of teams under pressure but we coped with that.
"Our possession was good and we created chances. We did all the things we have done all season.
"It was the first time we have played 4-4-2 this season as our strength is passing the ball and I thought we did that well in a shape that allowed us to defend.
"Two set plays cost us and that has been our Achilles heel this season. On another day we could have scored two or three."