Those who leave include forward David Ball, who spent last season on loan at League One side Bradford City and midfielder Darren Potter, who has been sidelined with a long-term injury for the last season-and-a-half.
Meanwhile, the club remain in discussions with wingers Anthony Forde, Jon Taylor, Ryan Williams and Joe Newell, who are out of contract in the summer, with Laurence Bilboe also in talks with the Millers hierarchy.
The club have also triggered an option in the contract of left-back Joe Mattock - to extend his deal by a further year.
Also released along with former Fleetwood man Ball and utility man Dominic Ball, who has spent the past two seasons on loan at SPL side Aberdeen, are winger Alex Bray and defender Emmanuel Onariase.
The club confirmed earlier this week that Akeem Hinds had penned a new one-year deal with the club.
Marek Rodak, Richie Towell and Zak Vyner will all return to their parent clubs.
Manager Paul Warne said: "I would like to take this opportunity to thank all the players who have left the club, and I would like to wish them well for the future.
"We have players leaving who played a significant role in our promotion in 2018 and would go on to represent this great club in The Championship.
"Their contribution to Rotherham United is greatly appreciated by all the staff and I am sure by the supporters."
Millers utility man Semi Ajayi has been named in the provisional squad for Nigeria's provisional squad for this summer's African Cup of Nations
Ajayi, who enjoyed an impressive 2018-19, has been named in a 25-strong party by coach Gernot Rohr.
The squad will take part in a training camp in Asaba from June 2-9 before a pre-tournament friendly against Senegal on June 16 in the Egyptian city of Ismaila.
Nigeria, who have won the Africa Cup of Nations three times, are in Group B alongside Guinea, Madagascar and Burundi.
Along named in the squad is midfielder Jon-Obi Mikel, who recently left Middlesbrough after a short-term spell with the club.