Besides the standard troops of the Centuries, the Legions have Auxiliaries. These troops are used as support and/or quick strike troops or support staff.
Non-Combatant auxiliaries are medics and surgeons, tailors and seamstresses, cooks, tanners, smiths and more. These people specialize in their talents and often are untrained in arms or bear very simple education in such. They are not soldiers pe se, even though they are legionaries. Twenty men out of every century (20 of 100) are non-combatants.
Archers, Sappers, Engineers
These men are still soldiers and fight as soldiers, but can be drawn out of rank and used for their specific talents whether it be as a hail of deadly arrows, an explosion of huge proportions or the creation of a bridge to get troops across a river.
Each legion has a unit of three hundred cavalry-men assigned to it. They work in thirty-man teams, or turmae. Three officers, or decurions, each command ten men, with one commanding the turma itself. Cavalrymen come from the ranks of the Ordo Equester of the city, or Knights, men who are not necessarily noble but may be wealthy.