This name, which was rare in the 1st cent., is mentioned several times in the NT:
1. The city treasurer, or steward, at Corinth who is included in greetings by Paul (Rom. 16: 23). In the municipal government of the city, which on a much smaller scale was similar to that of republican Rome, there were four senior magistrates, elected every year, who were assisted by two aediles, responsible for commercial and financial matters. An inscription from the middle of the 1st cent. CE on paving near the theatre names a certain Erastus as an aedile. He could well be the person mentioned by Paul, though he calls him an oikonomos which in the local government would have been of lower rank than an aedile. The suggestion therefore is that this Erastus was converted by Paul and became a member of the Church in Corinth, and that subsequently, in spite of his Christian faith, he was promoted to be an aedile. 2. A fellow traveller with Timothy (Acts 19: 22). 3. A fellow worker with Paul, who spent some time in Corinth (2 Tim. 4: 20).
Because of the rarity of the name, these may all be references to the same individual.