In 1947 he went on to study at the Nossa Senhora Aparecida Seminary, in Caxias do Sul, where he remained until 1953, and later graduated in Philosophy and Theology at the Pontifical Gregorian University.
On 16 November 1972, Moretto was appointed by Pope Paul VI as bishop of the Diocese of Cruz Alta, being consecrated by Dom Umberto Mozzoni on 28 January 1973.
On 21 January 1976, he was transferred to the Diocese of Caxias do Sul as coadjutor with the right to succession, taking office on 19 March 1976.
On 26 May 1983, during the pilgrimage of Nossa Senhora de Caravaggio, Moretto was appointed bishop of Caxias do Sul, succeeding Dom Benedito Zorzi, a role he would hold for 28 years.
Four days later, Pope Benedict XVI accepted his resignation due to age limit, and since then he had been Bishop Emeritus of Caxias do Sul.