Roger Paul Morin was born on March 7, 1941, in Lowell, one of six children of the late Germain J. and Lillian (Cregg) Morin. He attended elementary and secondary schools in Lowell, Dracut, and Boston. From 1962 to 1968, he attended Cardinal O'Connell Seminary in Boston and St. John Seminary in Brighton. He received a B.A. in philosophy from St. John's in 1966.

He worked in the New Orleans Archdiocese's Witness Program in 1967, and returned to New Orleans in 1968 and became director of The Center, an archdiocesan social service organization. Remaining director of The Center, he entered Notre Dame Seminary in 1968, where he earned a Master of Divinity degree in 1970. He was awarded a Master of Science degree in urban affairs by Tulane University in 1974.

Archbishop Philip M. Hannan of New Orleans ordained him a priest for the Archdiocese of New Orleans on April 15, 1971, in St. Therese of the Child Jesus Church in Dracut. After ordination, he was assigned to St. Henry Church in New Orleans. He was named associate director of the archdiocese's Social Apostolate in 1973, becoming director in 1975. From 1978 to 1981, with Archbishop Hannan's permission, he served as a volunteer special assistant in the office of the mayor. In 1981, he was appointed archdiocesan vicar for community affairs with residence in Incarnate Word Parish in New Orleans. He was named pastor of the parish in 1988 and served there until 2002.

In 1987, he directed the archdiocesan preparations for the visit of Pope John Paul II and in 1993 he coordinated the archdiocese's bicentennial celebration. On June 15, 2001, he was named vicar general and moderator of the curia of the Archdiocese of New Orleans.

Pope John Paul II named him Titular Bishop of Aulona and Auxiliary Bishop of New Orleans on Feb. 11, 2003. He was ordained bishop on April 22, 2003, in the Cathedral Basilica of St. Louis, New Orleans, by another archdiocesan native son, Archbishop Alfred C. Hughes of New Orleans. Archbishop Hughes was assisted by the two archbishops emeriti of New Orleans: Archbishop Philip M. Hannan and Archbishop Francis B. Schulte.

Bishop Morin was named Bishop of Biloxi by Pope Benedict XVI on March 2, 2009. Bishop Morin's episcopal motto is "Walk Humbly and Act Justly." Upon reaching the mandatory retirement age of 75 on March 7, 2016, Bishop Morin submitted his letter of resignation to Pope Francis. The Holy Father accepted his resignation on Dec. 16, 2016.

The bishop died Oct. 31, 2019, on his return from visiting family in Massachusetts. He was 78 years old.

Bishop Morin's survivors include his brother, Paul; his sisters, Lillian "Pat" Johnson, Elaine Joncas; and Susan Spellissy.

His Funeral Mass was celebrated Nov. 7 at the Cathedral of the Nativity of the Blessed Virgin Mary in Biloxi; he was buried in the Bishops' Cemetery, Biloxi.