Matsui had struggled since joining the rays as a free agent. In 34 games Matsui was 19-35 with two home runs.
Matsui had drawn the ire of Rays fans of late booing him unmercifully in his last few home plate appearances.
It is likely the end of the line on a great career for the 38-year-old Matsui.
Roberts was acquired in a trade yesterday with the Arizona Diamondbacks to play third base and serve as a replacement for Evan Longoria.
The Rays are said to be involved in talks with the Rangers and the Angels about RHP James Shields.