And there was also concern for fellow Lion Leigh Halfpenny who pulled out of the Magners League tie with a thigh strain.
Medical student Roberts was twice treated during the game before making way on 48 minutes and will see a specialist to asses any damage.
"It's the same shoulder I've had an operation on before so I'm seeing the specialist to make sure everything is Okay," said Roberts, whose Blues and Wales centre partner Tom Shanklin was ruled out of the tour to South Africa last week.
"I'm keeping my fingers crossed that it's just a 'stinger' injury but of course it's a concern with the Lions so near. I'd be lying if I said I wasn't worried."
Halfpenny withdrew from Sunday's game after pulling up during the warm up, although Blues head coach and former Lion Dai Young does not anticipate there being any serious issue with the youngster's fitness.
"Leigh felt his quad muscle before the game so we didn't want to take any risks," said Young.
"It was purely a precautionary measure to pull him out."