Bostock, Aidan Barlow and young defender Bobby Faulkner will be offered fresh terms.
Rovers also confirmed they will take up options on captain Tom Anderson and goalkeepers Louis Jones and Ben Bottomley when they announced their retained and released list on Monday.
John and Okenabirhie headline the departees.
Defender John, 22, impressed after joining Rovers initially on loan from Wolverhampton Wanderers but dropped down the pecking order before missing the majority of last season with a back injury.
Rovers will continue to support Okenabirhie in his recovery from a long term Achilles injury after the 26-year-old striker sat out last season in its entirety.
Dan Gardner, Branden Horton, Ed Williams, AJ Greaves and Lirak Hasani will also be released when their contracts expire this summer.
Ben Blythe is set to complete his permanent move to Championship side Swansea City.
Rovers boss Gary McSheffrey told Rovers’ official website: “It’s never easy having conversations with players who are leaving the club but we have made these decisions with how we want the squad to look next season in mind.
“Some of the players were unfortunate, however having had 34 players including loans with us at the end of the season, we have a clear vision of the size and make-up of the squad going forward.
“We would like to thank all the players leaving us for their efforts while with the club, and wish them well for their future careers.”