The left-back, 23, who has been a regular for the Shakers this term, beat the 5pm deadline to complete a move and cannot wait to get started.
He told the Millers' official website: "I'm delighted to be here first and foremost and looking forward to getting the team promoted.
"When I got the call about the interest from Rotherham I immediately thought I wanted to come here.
"If you look at the new stadium and fanbase, it's geared up for a higher division and I wanted to be involved in that."
- Sports & Recreation