The media reported the centre was set to join French club Racing Metro in Paris but Roberts has not yet said where he is going.
Roberts, who returns to the national side for Saturday's clash with Argentina having been out since April with cruciate ligament damage to his knee, hoped in a statement on Thursday that the decision would not affect his international career.
"This has been an extremely difficult decision, but I am absolutely certain it is the correct time for me to enter a new stage of my career," the Welsh Rugby Union quoted him as saying.
"My intention is to emerge from the experience of playing for a new team as a better rugby player and to broaden my personal horizons in a new environment."
Other Welsh internationals currently in France are James Hook, Gethin Jenkins, Lee Byrne, Luke Charteris and Aled Brew.
Scrumhalf Mike Phillips moved to French club Bayonne in 2011 and the back was dropped to the bench for Saturday's encounter.
"As professional players we work immensely hard and there comes a time when you know that a fresh environment will help you retain the sharp edge of determination required to remain a contender for top honours," said Roberts.
"I will complete my medical training in March and currently have the opportunity to step outside the academic environment for a couple of years before I take up my required hospital training period."