The Roman army was a professional army that men joined for a number of reasons. One of the main reasons for joining was conscription.
Men were drafted into the army between the ages of 18-46. Men between these ages were offered a secure job where they were fed and sheltered but had little say if they joined or not, especially in the early days of Rome. Times of crisis saw all men conscripted to fight and to protect Rome from attack.
The army specifically focused on 'landless city dwellers' to try and swell its ranks. These would be conscripted for between 20-25 years. People that wanted a certain position in government would have to spend time in the army.
Auxiliary volunteer usually came from the territories that Rome was looking to capture. These men were usually part time soldiers who were skilled in different forms of fighting such as archery and joined the army for safety and payment before the Romans entered an area.
Members of the army were paid usually on an annual basis and they would have received a pension after they retired from the army. This would have ensured they and their family were well kept. They would have also been given extras from time to time but these would have been expected to be shared with other soldiers in the army. Sometimes men who supervised the army would be ordered to be given land as payment. This was especially the case in new conquered areas that they could look after.
Legionnaires would be given citizenship during some periods of Rome's history which was a motivating factor for many to join.
There were many reasons to join the Roman army and in many cases the reasons changed over time as the army expanded and contracted.
