After ordination in the Cathedral of the Immaculate Conception, Port of Spain, by Archbishop Anthony Pantin on June 27, 1971, he went to the Pontifical University of St. Thomas Aquinas (Angelicum), Rome, where he obtained the Licence in Theology.
After Rome, he returned to Ireland where he successfully completed a course in radio and television production and received a diploma in communications.
On his return to Trinidad and Tobago he spent his first two years of ministry at St Theresa’s, Woodbrook, Port of Spain, under the direction of the future master of the Order of Preachers, Rev.
On October 28, 1989, his appointment as the first bishop of the newly created Diocese of Kingstown in St Vincent and the Grenadines was announced in Rome.
[2] Bishop Rivas has served as the chairperson of the Family and Life Commission for the Antilles Episcopal Conference (AEC), as a member of the Commission for Social Communications (Decos), of the Council of Bishops of Latin America (CELAM) and the chairperson of the National Committee Against Violence in St Vincent and the Grenadines (SVG).
He also served as visitator of the Regional Seminary of St John Vianney and the Uganda Martyrs and as a member of the Pontifical Council for Latin America (CAL).