What are the roles of a Catholic bishop?

Catholic Answer

A bishop is a successor of the Apostles, he has received the fullness of Christ's priesthood. His most distinctive and unique role is ordination - to ordain priests and other bishops. In most cases, a bishop is in charge of a diocese, even if it is only titular - there are over two thousand ancient Catholic dioceses and archdiocese which have been destroyed by the Moslems; the titles are now given to auxiliary, coadjutor, and other Bishops who do not have a residential see.

A Bishop may only ordain another Bishop with express permission from the reigning Pope. The Bishop is the head and fullness of the Catholic Church in his diocese, he wears a ring to symbolize his authority and carries a shepherd's staff for the same reason.