Earlier in the week Roberts tweeted that his return to rugby was imminent after five months out following wrist surgery.
But Cardiff Blues head coach Young, a Lions legend himself with three tours, has sounded a note of caution.
Although Young was delighted to have his star centre back in full training he does not anticipate having Roberts match fit for the back-to-back Heineken Cup clashes with Northampton.
He instead reckons Roberts will be back for a busy festive period in the Magners League.
"He's probably swallowing his foot at the minute," said Young.
"He announced his return to the world but he's retracting his statement a bit really.
"He's only had the all-clear that he can start. Fitness won't be a problem, he's also done plenty of skills. It's just a case of getting some contact in.
"We're not going to rush him back. It's good news but it's a long shot to say he could be back for the second European clash with Northampton.
"But I'm sure come the Dragons and Ospreys games he will be figuring."
Roberts has not played a game of rugby since going on Wales' summer tour of New Zealand in June and underwent wrist surgery in July.