But after a period of rest, the Welsh international recently returned to Cardiff for an operation, ruling him out for two months.
It leaves him a major doubt for his country's first Test against South Africa on November 9 which is then followed by games against Argentina, Tonga and Australia, as revealed by Racing assistant coach Laurent Labit.
"Jamie has reported back to us after ten days in Cardiff for the operation," said Labit.
"He will be out for at least two months after surgery and will hopefully be back playing some time in November, but he will probably miss the Wales Tests."
Former Cardiff Blues Roberts joined up with his new French side after the Lions tour, and Labit admitted the enforced rest may come as a bonus for the 26-year-old, who also injured his hamstring in Australia.
"Maybe this [lay-off] is not such a bad thing for Jamie because he was so tired after the Lions tour and finishing his medical studies," he added.
"He really wanted to play as soon as he arrived at Racing but he was mentally drained.
"He picked up an injury during the Lions tour in Australia and come back tired. So hopefully we will see the best of him in the second half of the season."