"The rejection of the bid reaffirms the importance of Matthew Mills to Doncaster Rovers. Both the management and Board feel that Matt is integral to the progress of the club," Ryan told the club's official website.
"The Club have had great interest in a number of our players, but the Board and management want to build a side that can compete at the top of the Championship and beyong.
"We hope that the fans appreciate the level of commitment by the Board to not make Doncaster Rovers a 'selling' club.
"We now hope that the fans come out to support the club and to back the Board in their ambition."