Mitchell Rozanski was born in Baltimore, Maryland. He is of Polish descent and his surname means in Polish rose. He attended Sacred Heart of Mary School in Dundalk, Our Lady of Mt. Carmel High School in Essex, and the Catholic University of America in Washington, D.C. before entering the Theological College at the Catholic University, where he received seminary training.
He was ordained to the priesthood by Archbishop William Borders on November 24, 1984.
His parish assignments included appointments at St. Michael Church in Overlea in 1984 and the Cathedral of Mary Our Queen in 1985. He was appointed Associate Pastor at St. Anthony Church in Baltimore in 1985 and at St. Isaac Jogues Church in the same city in 1990. He was named administrator of Holy Cross Church and of St. Mary Star of the Sea Church in Baltimore in March 1993, before being appointed pastor there in the following October. In January 2000, he was appointed temporary administrator of Immaculate Conception Church in Towson and in June of that year he assumed the same duties for St. John the Evangelist Church in Severna Park, where he was named pastor on November 28, 2000.
On July 3, 2004, Rozanski was appointed Auxiliary Bishop of Baltimore and Titular Bishop of Walla Walla by Pope John Paul II. He received his episcopal consecration on the following August 24 from William Cardinal Keeler, with Bishops William Newman and W. Francis Malooly serving as co-consecrators. He selected as his episcopal motto: "Serve The Lord With Gladness."
As an auxiliary bishop, Rozanski also served as Vicar for Hispanic Ministries and as Seton Vicar, in which position he ministered to the parishes in Anne Arundel, Howard, Carroll, Frederick, Washington, Allegany, and Garrett Counties.
The United States Conference of Catholic Bishops announced on April 18, 2011, that he would be named to succeed Edward U. Kmiec, the Bishop of the Buffalo, New York, as incoming Roman Catholic Co-Chairman of the Polish National Catholic-Roman Catholic dialogue, due to Bishop Kmiec's impending retirement. He was named to the post by Archbishop Wilton Gregory of Atlanta, Georgia, and Chairman of the U.S. Bishops' Committee for Ecumenical and Interreligious Affairs. On November 12, 2013, he was elected to chair the USCCB Committee on Ecumenical and Interreligious Affairs beginning in 2014.
On June 19, 2014 Pope Francis named Rozanski the ninth bishop of the Diocese of Springfield. He was installed as the Bishop of Springfield on August 12, 2014.