There Catholics have a rather close relationship with the Orthodox Church, confession more widespread in the country, since the two Christian realities coexist for many centuries, and especially after the Second Vatican Council.

There is also the Greek Byzantine Catholic Church, in communion with the bishop of Rome from the nineteenth century, which has about 3,000 faithful in Greece.

He decided to follow his priestly vocation, so in 1962 he moved to Rome as a student at Sant'Atanasio College of the Greek Church and the Pontifical Gregorian University where he earned a BA in philosophy and theology.

Then, at the end of six years of stay in Rome, he returned to his homeland, where on 21 July 1968 he was ordained a priest for the Roman Catholic Diocese of Syros and Milos.

Rossolatos has held various positions in the Commissions of the Holy Synod of Catholic Bishops of Greece, in particular liturgical, including: Chancellor of the Curia, a member of the Ecclesiastical Court, and religion teacher at many public schools, contributor to courses in diocesan marriage preparation and member of Committee on Divine Worship.