What role did priests and bishops play in the early christian church

The sacrament of holy orders is conferred in three ranks of clergy: bishops, priests, and deacons.

Bishops (episcopoi) have the care of multiple congregations and appoint, ordain, and discipline priests and deacons. They sometimes appear to be called "evangelists" in the New Testament. Examples of first-century bishops include Timothy and Titus (1 Tim. 5:19–22; 2 Tim. 4:5; Titus 1:5).

Priests (presbuteroi) are also known as "presbyters" or "elders." In fact, the English term "priest" is simply a contraction of the Greek word presbuteros. They have the responsibility of teaching, governing, and providing the sacraments in a given congregation (1 Tim. 5:17; Jas. 5:14–15).

It's quite long, but hope it helps :)