Sato was selected by the
San Antonio Spurs in the
2004 NBA draft, and was subsequently waived on February 24, 2005. After being drafted by the Spurs, Sato played in the
Italian Second Division with
Sicc Cucine Jesi. He was the league's second-leading scorer in the 2005–06 season, averaging 25.5 points per game, and also adding 7.5 rebounds per game. In Romain's three playoff games that season, he averaged 35 points and 14.6 rebounds. From there, he went to
FC Barcelona to play in the 2006
Spanish ACB League playoffs. Sato then returned to Italy to play in the top
Italian League with
Montepaschi Siena for the 2006–07 season. In his first season with Siena, he helped Montepaschi to win the
Scudetto (Italian Championship), and he then went on to win three more
Scudetti with Siena. He was named the
Italian League MVP in 2010. In July 2010, he signed a three-year contract with
Panathinaikos. In the summer of 2012, he signed a two-year contract with
Fenerbahçe Ülker. He left them after one season. In August 2012, he signed a one-year deal with the Spanish team
Valencia Basket. On July 1, 2014, he re-signed with Valencia Basket for two more years. ==National team career==