Keegan, 32, has been with Doncaster since 2011 and made 145 appearances, although only 10 this season.
Gary McSheffrey, Aaron Taylor-Sinclair, Joe Pugh and Joey McCormick are also leaving on a free this summer.
Ross Etheridge, Cedric Evina, Mitchell Lund, Harry Middleton and Andy Williams have been made available for transfer.
Meanwhile, Conor Grant has returned to parent club Everton after his loan expired, and Rovers say they will not pursue a permanent move at this time.
Second-year scholars Lloyd Henderson, Josh Barker and Matthew Gains have left the club.
Paul Keegan heads a list of five players released by Doncaster Rovers, who have placed a further five on the transfer list.