The Iceland international is the Royals' longest serving player - making 239 appearances since 2003 - but had not played since sustaining a hamstring injury in March 2010.
Speaking to the club's official website, Ingimarsson said: "I feel good now, though I'm not going to lie, I'm very tired.
"It was a difficult six or seven months for me, not knowing what's going to happen with your injury.
"Doncaster is always a tough place to go, they play the ball about really well and you have to be focused.
"It was good to be back, I enjoyed playing and the team did really, really well."