Joseph La Rocque became Titular Bishop of Cydonia, and he later succeeded Jean-Charles Prince as Bishop of Saint Hyacinthe, a Latin rite suffragan located in Quebec.
In 1852, La Rocque accompanied Coadjutor Bishop Jean-Charles Prince to Rome as his secretary. When Prince was named Bishop of the Diocese of Saint-Hyacinthe, La Rocque was appointed Titular Bishop of Cydonia and Prince's successor as Coadjutor Bishop of Montreal. In 1860, he was transferred to succeed Prince as Bishop of Saint-Hyacinthe|Saint-Hyacinthe. The Roman Catholic Diocese of Saint-Hyacinthe (Latin: Dioecesis Sancti Hyacinthi) (erected 8 June 1852) is a Latin rite suffragan of the Metropolitan Archdiocese of Sherbrooke in Quebec, (predominantly francophone) Canada. 
