The Roselle Catholic High School Lions[5] compete in the Union County Interscholastic Athletic Conference, which includes public and private high schools in Union County and operates under the supervision of the New Jersey State Interscholastic Athletic Association (NJSIAA) and was established as part of a reorganization of sports leagues in Northern New Jersey.

[15] The 1978 team won the Parochial A state title with a 3–1 win against Camden Catholic in the championship game played at Mercer County Park.

[19] The girls volleyball team won the Non-Public state championship in 2006, defeating runner-up Immaculate Heart Academy in the final match of the tournament.

[22] The team won the 2018 Non-Public B title with a 63–61 win against Ranney School on a basket scored with just over six seconds remaining in the championship game.

[23] The team came into the 2013 Tournament of Champions as the top seed and finished the season 25-5 after winning the program's first ToC title with a 78–54 win against fifth-seeded Newark Tech High School in the semifinals and 65–49 against number-two seed St. Joseph High School of Metuchen in the championship game.