How was the Roman empire able to support its armies and public services

By protecting them with their allies and army

Taxes were placed on people who had been conquered.

Explanation:

Throughout the history of ancient Rome, many different tax systems existed. However, taxes were always an important component of the empire, and the main way in which the Roman Empire was able to support its armies and public services. One of the most important taxes the empire relied upon was the tributum. This taxed citizens based on their material wealth. This tax, however, was usually only placed on people who had been conquered (as opposed to residents of Rome).