He struck in the 83rd and 90th minutes to give his side their first win of the season but for long periods of the match the Swansea performance was far from those reached last season by the play-off finalists.
Swansea included new signing Dennis Lawrence at centre-back and Trundle partnered Rory Fallon up front, leaving Leon Knight on the bench.
Rovers, managed by former Swansea captain David Penney were without the suspended Wales international Gareth Roberts, but summer signing Bruce Dyer had recovered from injury to take a place on the bench.
Swansea made all the early pressure and Willy Gueret in the home goal never had a touch until a Darren Pratley back pass in the eighth minute.
They had a scare when Lawrence and Gueret collided as Mark McCammon challenged for a high ball in the danger area. As both Swansea players fell to the ground McCammon's side-footer drifted wide of the far post but the referee had already blown in the home side's favour.
Trundle almost broke the deadlock in the 27th minute but a quick turn followed by a drive saw his shot deflected over the Donny cross-bar for a fruitless corner.
Swansea had controlled midfield as the first half drew to a close but Trundle and Fallon rarely made headway against a solid Rovers back-line while even with Lawrence in a central position the Swans still looked vulnerable to a counter-attack.
Kevin McLeod picked up a Leon Britton pass ten minutes after the break and rifled a shot that had the Doncaster keeper sprawling to his right to push away.
The visitors were quick on the break and the cross from Jason Price was met by McCammon but his header flew wide.
Trundle had a gilt-edged chance in the 75th minute but Blayney came out to make a magnificent block and concede a corner.
Before the kick was taken Kenny Jackett made a double substitution with Adebayo Akinfenwa replacing Fallon and McLeod making way for Tom Williams.
Suddenly Swansea increased the tempo and the breakthrough came in the 83rd minute when Trundle brushed aside two tackles before lashing the ball beyond Blayney and into the net.
Right on time Trundle doubled the score when he beat the offside trap before sliding his shot beyond the diving Blayney.