[7][8] In August 2022, he signed a short-term developmental contract with HFX Wanderers FC of the Canadian Premier League.

[11][12] However, shortly after he returned to the Wanderers after an injury to goalkeeper Kieran Baskett and on October 9, he made his professional debut against Forge FC.

[16][17] In August 2023, De Rosario was loaned to Canadian Premier League side York United until the end of the 2023 season.

[18][19] He made his debut on August 12 against Forge FC, playing the full match in an eventual 3–3 draw at Tim Hortons Field.

[25] On February 7, 2025, De Rosario signed a two-year homegrown player contract with Toronto FC in Major League Soccer, with options for 2027 and 2028.