The 28-year-old winger’s deal runs out next month and the club are not offering him a new deal.
Miller, who arrived from Hamilton in 2020, made 39 appearances for the Millers over the course of two seasons.
He did play a crucial part in this season’s success as Paul Warne’s side won a promotion and cup double, with his tricky displays in the autumn helping them surge to the top of League One.
Troublesome hamstring injuries after Christmas restricted his availability and the club have decided to part company.
Miller announced his exit on Instagram, by posting: “Two years done and finished like that.
“I would like to thank all the staff and fans for making me feel so welcomed from the start to the end. And to all my teammates / brothers. What a group!
“Wishing you all the best next season.”
The Millers are expected to announce the rest of their retained list on Monday where the fate of a host of players will be announced.
Midfielder Jamie Lindsay is one of those out of contract, though the club do have an option to extend.
They are thought to be keen on agreeing a longer-term deal.
Lindsay endured a stop-start campaign last term due to injury but attracted interest from Portsmouth in the January transfer window.
But Lindsay said: “I hope to be here next season. I’m happy here and I love the boys.
“I’ve had a good three years, although this one hasn’t been the best personally.
“Every player wants to play games. It was tough for the gaffer to put me back in because of how well the team were doing.
“At the end of the day, it’s a team game. I understood that me not being selected was part and parcel of that.”
Warne previously said he would like up to nine new players to come in this summer: “It is a very, very difficult ask but we need to recruit seven, eight, nine players who are better than the ones we have.”