The union eventually took place with Jordan Purcell appointed bishop of the united see of Cork and Cloyne in 1429.

[citation needed] This see was founded by St. Fachtna, and the place-name was variously known as Roscairbre (Rosscarbery) and Rosailithir (Ross of the pilgrims).

In 1207, the Norman King, John of England, granted the cantred of Rosailithir to David Roche, regardless of the claims of the native chief, the O'Driscoll, but the episcopal manors were left undisturbed.

The number of parishes was 29, divided into 3 divisions; and there was a Cistercian abbey, Carrigilihy (de fonte vivo); also a Benedictine Priory at St. Mary's, Ross.

However, he was translated to the united bishopric of Cork and Cloyne in 1490; was again a victim of political intrigues, and died a confessor at Ivrea in 1492, being beatified in 1895.

Developing from the Bishop's Course in Theology, recently the Certificate in Christian Studies (validated by St. Patrick's College, Maynooth) has been delivered in the Diocese.