Having impressed for Wales on the summer tour of New Zealand, 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 the 24-year-old on the sidelines until earlier this month but he came of the bench against Northampton in the Heineken Cup two weeks ago.
Roberts then finally returned to the Blues starting XV against their bitter rivals and immediately impressed his coach with a typically powerful display in both attack and defence.
"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."
The only downside for Roberts during the win over the Ospreys was yet another injury worry after he received treatment in the second period.
But Young quickly dismissed the significance of that scare, especially as Roberts was able to continue playing for the full 80 minutes.
"Jamie had a bit of a stinger but he's fine. He diagnosed himself before the physio even got to him!" added Young.