Veteran pair Coppinger and Blair are among five senior players set to see their current deals expire at the end of the month, but will be offered renewals by manager Darren Moore.
However, the financial impact of the shutdown of football due to the Covid-19 pandemic and the on-going uncertainty over next season have ensured that only reduced terms will be offered to Coppinger and Blair at this stage, until the club’s financial position is more secure.
Sadlier, who turned down a contract offer earlier in the year is set to be released - along with Devante Cole and Alex Baptiste.
Moore has previously expressed his desire to keep Sadlier at the club.
But the 25-year-old and his advisers are thought to be awaiting potential offers from Championship clubs after his impressive season with Rovers in which he finished as top scorer.
Rovers have declined the opportunity to take up an extra year in the deal of striker Cole, who joined the club in January from Wigan Athletic.
Cole signed a six-month contract with the option of a further year. The 25-year-old leaves having failed to score in nine appearances for Rovers.
Baptiste has also been released after an injury-hit season at the Keepmoat.
The veteran defender ruptured his Achilles tendon in only the second match of the 19/20 season. He regained his fitness in February and made three matchday squads before the season was halted.
Academy graduates Danny Amos and Louis Jones are also thought to have been offered new contracts while young midfielder AJ Greaves is understood to have agreed a new deal with the club.
Six remaining members of Rovers’ U23 group are set to be released at the end of their deals this month, including Alex Kiwomya.
The striker endured a difficult three-year spell at Rovers after joining from Chelsea. He contracted the auto immune disorder Guillain-Barré syndrome shortly after his arrival which kept him out of action for much of the 17/18 season.
He managed only 20 appearances for Rovers in three years and had loan spells with Chesterfield and Chorley in the National League.
Also on the released list from the U23s are Shane Blaney and Max Watters, who both made senior appearances in the 19/20 season, plus defender Rian McLean and forwards Rieves Boocock and Myron Gibbons.
Rovers have yet to confirm if they will operate with an U23 squad next season.