The Roman Legion Had a Large Entourage
When it comes to the Roman Legion they were not on their own on the battlefield. Even once the requirements had been loosened and all members of the legion (citizen and non-citizen) were merged together in the same units, there were still auxiliary troops that accompanied the Romans to ensure that the army did not want for anything. In the beginning when conscription and volunteer requirements were strict, the auxiliary troops would be pulled from tribes and put into troops that would fight beside the legion. Men pulled from mounted tribes would become part of an auxiliary that would fight beside the Cavalry. Other tribe members would be put into auxiliaries that would fight beside the infantry. Eventually both these groups were merged into singular legions but there were still others that traveled with the Legion to ensure that the army could continue on in battle.
There were surveyors that would travel ahead of the main army in order to find a main site for the army to find the best place to camp that night. The surveyors were part of a group of men that traveled with the Roman Legion that were known as immunes. These men included those who were excused from fighting because they were pivotal to the war effort in other ways. The immunes included medics, carpenters, veterinarians, armorers, priests and soothsaysers and even hunters. These men were necessary for keeping the army fed, well supplied, in good health and they helped build the weapons that were needed in siege warfare, like catapults.