Sheridan, 32, signed for The Robins from Altrincham back in 2018.
The central midfielder started his career with Bolton and went on to play for Stockport, Chorley and NPL side FC United.
He made 143 club appearances, scoring 13 goals and has more recently been stifled by injury, forcing him into the decision to take a break from the sport.
Also playing in central midfield, Tomsett, came through the youth setup with Blackpool and broke into the first-team in 2011.
The 29-year-old had spells with Hyde United, Flyde and Curzon Ashton, before he put pen to paper with The Robins in 2017.
Tomsett made 178 appearances, netting 28 times for Ashton, including a goal against Grantham Town in the Evo Stik Playoff Final in the 2017/18 term.
Ashton United are currently 11th in the Pitching In Northern Premier League and they make a trip to Radcliffe Borough for their fixture this Saturday.
Photo credit Ashton United
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