Roberts had been ruled out of action since undergoing wrist surgery in July to repair damage initially sustained during the 2009 Lions tour of South Africa.
That kept Roberts on the sidelines until earlier this month but he came of the bench against Northampton in the Heineken Cup two weeks ago.
And Roberts returned to the Blues starting XV as they triumphed 27-25 over the Ospreys in the Magners League.
"Jamie was outstanding," said Young. "He was really physical with the ball in hand and in defence. He has brought real energy and enthusiasm to training since he has come back.
"It was important to get the win and to beat our local rivals and the reigning Magners League champions makes it that little bit sweeter.
"But again it was not the full performance, the last 20 minutes we were hanging on by our toenails. We're still not playing anywhere like we can and there's a lot more to come from us."
Roberts, the 2009 Lions' Man of the Series, gave Young a fright when he received treatment in the second-half but the medical student shook off the bump and was able to finish the game.
"Jamie had a bit of a stinger but he's fine. He diagnosed himself before the physio even got to him!" added Young.