The 27-year-old was joined by Mike Phillips, Dan Lydiate and Jonny Sexton - who scored Racing's only points with a penalty - in the starting line-up but they failed to get to grips with Quins who are now second in Pool 4 of the Heineken Cup.
But Roberts, who scored the final try during the Lions' decisive victory over the Quantas Wallabies down under, insists his injury troubles are behind him.
"The injury is good. I've had good rehab, the physios have done a good job and it feels great," he said.
"It's a bit disappointing with the result, but I haven't been playing for 13 weeks so it's good to be back there playing rugby."