As Rome started to conquer small villages and towns, they build up a larger army. After a while, Roman commanded a large territory and had a large army.The way Rome were such great conquerors, is because they had a well trained and very organized army. The little villages and towns were powerless against the Romans.
The army was divided into legions. Legions consisted of 4,000 men/legionaries. There were 2 main types of foot soldiers:they were legionaries and auxiliaries. They were the same accept for that legionaries were Roman citizens and auxiliaries were not.In fact, auxiliaries were sent out into the front lines of battle. Many were killed or wounded. But who cares, they aren't Roman citizens! Centurions were men who led another 100 men into battle.
Roman soldiers/legionaries were expected to be able to be good engineers and builders. During peace time legionaries would be the workers that build bridges, buildings, etc. Legionary soldiers were very important for Roman life.
Credit to: ukcaelo