The versatile 22-year-old was in his first year as an inside centre having previously played full back and wing and Young feels his young charge has the potential to get even better.
"As good as he is now, I still feel there's a lot more to come from him," said Young, who himself toured with the Lions in 1989, 1997 and 2001.
"He's only had a season in the game at the top level in that position," Young told the Western Mail.
"Let's hope Jamie realises that. It's important that's emphasised to him.
"He's world-class now, but there's no doubting he can be better again."
Having started both the first and second internationals against the Springboks last month, Roberts missed the third and final Test in Johannesburg because of a wrist injury.
Initial prognosis led to fears that he may be forced into a substantial lay off, but a scan has since revealed that the medical student should be fully fit by the end of September.
And, with Roberts now having made a name for himself on the world stage, the 2009/10 campaign is one in which his club coach will be reminding him of the need to set even higher standards.
"Let's all celebrate his performances with the Lions and we should be very proud of them, but it's our job to keep on pointing out things which he can improve," added Young.
"Hopefully he will look to improve and be that better player and I'm sure he will.
"He knows he's going to be targeted in games and he understands that. We've got to protect him a little bit off the field because he's certainly going to attract the media attention and that's something he enjoys as well.
"As good as he is - and he's a phenomenal player at the minute - he can still improve his game and take himself to another level again."