Rousselet ran his first race in the Continental Cup in December 1998 in Ulrichen , which he finished classically in 18th place over 15 km. In the World Cup he made his debut in December 2000 in Santa Caterina and finished 77th in the 15 km freestyle. He got his first World Cup points in January 2001 in Soldier Hollow with 30th place in the 30 km mass start race and 27th place over 15 km classic. At the 2001 World Championships in Lahti , he came in 44th place in skiathlon , 40th place over 50 km freestyle and 33rd place in sprint. The following year, at the Winter Olympics in Salt Lake City, he finished 47th in the 30km mass start race, 35th in the skiathlon and eighth place in the relay. At the 2003 World Championships in Fiemme Valley , he came in 60th place over 15 km classic, 47th place over 50 km freestyle and 11th place with the relay. In February 2004 he won his only World Cup victory with the relay in La Clusaz and won the 76 km Worldloppet run Transjurassienne . After two placements in the World Cup within the points at the beginning of the 2004/05 season, he came in Lago di Tesero with third place with the relay again on the podium. This was followed by three more places in the points and he finished 77th in the overall World Cup at the end of the season. His best results at the 2005 World Championships in Oberstdorf were 25th place over 15 km freestyle and sixth place with the relay. At the beginning of the following season he won second place with the relay in Beitostølen . In the further course of the season he achieved his first and only top ten results in the individual World Cup with ninth place in Canmore and eighth in Lago di Tesero in the 30 km mass start race. His best results at the 2006 Winter Olympics in Turin were 18th place over 15 km classic and fourth place with the relay. He finished the season in 33rd place in the overall World Cup and in 21st place in the Distance World Cup. The following season he finished 42nd in the Tour de Ski 2006/07 . With the 13th place in the 11 km freestyle he achieved his best result of the season in the individual World Cup. In February 2007 he finished second with the relay at the World Cup in Davos . His best placings at the 2007 World Championships in Sapporo were 38th place over 15 km freestyle and fifth place with the relay. In the 2007/08 season he came in the points four times in the World Cup. At the Tour de Ski 2007/08 he came in 38th place. In January 2008 he started in Klosters for the first time in the Alpencup . He won the classic 10 km and was third in the 15 km mass start race. In the following season he finished 30th in the Tour de Ski 2008/09 and in January 2009 got his last World Cup points with 25th place over 15 km classic in Otepää . At the 2009 World Championships in Liberec , he came in 27th place over 15 km classic and ninth place with the relay. In his last active season in 2009/10, he mainly took part in ski marathon races. He finished ninth at the Transjurassienne and won the 42 km freestyle run in the Gsieser Valley .