Bosco granted him and another named Roccheti the cassock on 3 October 1853. Rua made his first profession on 25 March 1855 in the new Societá di San Francesco de Sales (Society of St. Francis de Sales) which Bosco was then forming; Rua was among its first members. For over the next three decades he was Bosco's closest collaborator in the development of the congregation. The death of Don Bosco's mother in 1856 prompted Rua to bring his own mother to live at the oratory where she remained for the next two decades. In 1858 he accompanied Bosco to Rome to seek official authorization for the congregation. He served as the first spiritual director for the congregation from 1859 even before his ordination to the priesthood which was celebrated on 29 July 1860; Monsignor Giovanni Balma ordained him. In 1859 he had been ordained a subdeacon and then raised to the diaconate on 24 March 1860.