As a redshirt freshman there in 2019, he recorded 15.5 sacks and won all-conference honors and was named ACC Defensive Rookie of the Year.

Born to Haitian parents from New York, Rousseau attended Champagnat Catholic School in Hialeah, Florida.

[2][3] Rousseau played in the first two games of his true freshman year in 2018 before suffering a season-ending ankle injury and redshirted.

[16][17] In his rookie season, Rousseau finished with four sacks, 50 total tackles, one interception, four passes defended, and one forced fumble.

[19] His best performance of the year came in week 14 against the New York Jets, in which he recorded 2 sacks, including a forced fumble, and a pass defensed, contributing to a 20–12 Buffalo win one week after the team's leading pass rusher Von Miller suffered a season-ending knee injury against the Detroit Lions on Thanksgiving.