Non-combatants

The non-combatants weren't people who sat on the sidelines while the battle raged on, but served more as a backstage crew. 

Often slave and servants served as the Calones.  The Calones were people who performed menial tasks such as being clerks, secretaries, maintenance workhorses, smiths, and sometimes cooks.  Mercatores, Latin for "merchants", bought, sold, and traded booty with the soldiers.  Their tents resembled pawn shops.  The Muliones were slaves specialized in caring for pack animals such as horses, mules, cows, and other beasts of burden.  They tended all the animals regularly.  The Fabri were engineers and architects.  They were responsible for the strength and functionality of buildings.  The Exploratores and Speculatores were considered the eyes of the army.  They were the people who scouted out the territory ahead of time.  They would be able to move days ahead of the army, and tell them the landscape's advantages ahead of time.  These people were mounted and considered part of the cavalry.

The Roman Legion

This was the large unit of people that was able to take on very large groups of opposing forces.  It was made up of many smaller groups, grouped into bigger and bigger ones.  The lowest unit was the Pedites, the single armed soldier.  Next would be the grouping called a Centuria, a pack of 100 men led by a Centurion.  Two Centuria would team up to form a Manipulus.  A Cohors would be made by binding 3 Manipuli together.  A legion would be formed by getting together 10 Cohorts.  The legion would be led by a general.

When Caesar was commanding his legions, he made them smaller to make them easier to maneuver. His century unit only contained 60 men, instead of the standard 100. This changed the amount of men per legion drastically, from the standard 6,000 to a smaller 3,600.

Standard Bearer

The people were a lot like the mascots for the army.  They would hold up a symbol to unite the soldiers, and lead them into battle.  The Aquilifer was the man who held the Aquila (eagle), the symbol of Roman Army.  This man would be carried by the Aquila into battle and lead the legion to victory.  There were many things like the Aquila found in battle.

The first of which was the Vexilla, this acted as a flag to rally small groups of soldiers.  The Imaginifer would hold a statue-model with medallions hanging from it.   Also found were the Signifers who were very educated men who stood in front of a Century, and the Draconius, a dragon-head with a fabric tail made to whistle in the wind.