Cooper has been ruled out of action for up to six weeks due to a knee injury he suffered against Sheffield United in the Yorkshire derby last weekend, according to BBC Sport.
The 27-year-old defender has undergone an operation, and his Leeds team-mate and striker Roberts, who can also operate as a striker, has send him a message on Twitter.
Blow for Leeds United
Cooper is one of the best and most important players in the current Leeds team, and the injury to the 27-year-old will be a blow to the West Yorkshire outfit.
However, Leeds head coach Marcelo Bielsa has shown time and time again this season that he can come up with solutions when there are injury problems in his squad.
Roberts joined Leeds from West Bromwich Albion in January 2018 for an initial transfer fee reported by The Yorkshire Evening Post to be worth £2.5 million.
The 19-year-old Wales international striker has made seven starts and provided one assist in the Championship for Leeds so far this season, scoring three goals and providing one assist in the process, according to WhoScored.