The goalkeeper was out of contract at the end of last season, having signed a short-term deal in November 2020.
He joined as third-choice stopper behind Jamal Blackman and Viktor Johansson and did not make a first-team appearance.
However, with Blackman returning to his parent club Chelsea, boss Paul Warne offered the 25-year-old the chance to stay in South Yorkshire and fight for the number one shirt.
With a return to pre-season training still a few weeks away, Vickers is glad to get his future sorted early and wants to be part of a promotion push next season.
“Last year I signed quite late, so it is a massive bonus to have everything sorted out early this time around,” Vickers said.
“It really helps knowing exactly where I’m going to be next season and not having to worry about my future, I now can’t wait to get going for pre-season.
“We’d have loved to have stayed in the Championship, but it is a new year and a new challenge. We’re looking forward to seeing how we progress this season.
“The aim is to always finish as high as we can, the last two times we’ve gone down we’ve managed to come straight back up, so I’m sure that will be the aim again this year.”
The Millers are still waiting on an answer from right-back Matt Olosunde regarding a new contract.
The American was offered fresh terms at the end of last season, but has yet to put pen to paper.