A native of Cap-Chat and the son of Wilfrid Roy, Joseph Sasseville Roy married Hélène, the daughter of Trefflé Baillargeon, in 1920. He ran unsuccessfully in the riding of Abitibi for a seat in the Legislative Assembly of Quebec in 1927 and 1931. Roy distanced himself from the Conservatives in 1941 after disagreeing with them on the subject of conscription. He was also unsuccessful in his re-election bids to represent the Gaspé constituency in 1945 and again in 1949. During World War II, he was criticized by the Canadian military for raising the issue of German U-boat attacks in the Gulf of Saint Lawrence. He wished to ensure that merchant ships were being protected; the military wished to prevent information leaking back to the enemy.