The Belgian reportedly had a heart attack in Mons and paramedics were unable to resuscitate him.
Roussel played for Coventry at the turn of the millennium, initially impressing on loan in 1999-00, he was signed on a permanent basis for £1.2 million from Belgian side Gent.
Roussel scored six goals in his first season in the Premier League, and had formed a promising partnership with a young Robbie Keane.
However, Keane moved in the summer of 2000 to Inter, and Roussel never displayed the same kind of form he showed in his first campaign.
He fell out of favour and was soon sold to Wolves, who were then playing in the Championship.
Injuries played a part in his time at Molineux, and he could never replicate that golden season at Coventry.
Roussel then went on to become something of a journeyman after leaving the Midlands in 2003, playing for clubs such as Genk, Rubin Kazan, Standard Liege and Brescia among a host of others.
He earned three caps for the Belgium national side, all coming in 2003.
He retired from the game in 2015 aged 37.