Sullivan, 43, was in inspired form throughout the promotion clash making a number of expert saves to keep Doncaster top of npower League One.
The former Tottenham, Leeds and Chelsea goalkeeper only arrived back at his parent club on Friday after a loan spell at AFC Wimbledon was cut short due to an injury to regular number one Gary Woods.
Flynn said: "Bringing Neil back was a big boost and he was absolutely magnificent.
"It was like having a young Neil Sullivan back and he played a big part in the result. It is almost worth a goal having a keeper like that. He made a great save in the first half and showed his experience by getting in good positions - it was exactly what we wanted."
After watching his side fall to their fifth straight defeat, Bournemouth boss Eddie Howe said: "I thought we deserved to win.
"It is the story of our recent results. The ball just isn't bouncing for us at the moment, but I was really pleased with the performance.
"It is not a nice feeling, but we will role our sleeves up.
"We have got to bounce back there are massive games coming up and we can still achieve something this season.
"We may look back on this as a turning point for us."