Stanley made 34 appearances after joining Rovers from Morecambe last summer, but only played 11 times following Mark McGhee's appointment to succeed Paul Buckle as manager.
The 29-year-old scored his only goal for the Pirates in March's 3-2 defeat at Northampton.
A statement on the club's official website read: "We would like to take this opportunity to thank Craig for his efforts during the past season and wish him every success in the future."







