The Roman legionary was a professional soldier of the Roman army after the Marian reforms of 107 BC. Legionaries had to be Roman citizens under the age of 45 at enlistment. They enlisted in a legion for twenty-five years of service, a change from the early practice of enlisting only for a campaign. The last five years were on veteran lighter duties.

On the march in unfriendly terrain, the legionary would be loaded down with armour commonly (lorica hamata), (lorica squamata), and 1st-3rd century (lorica segmentata), shield (scutum), helmet (galea), two javelins (one heavy pilum and one light verutum), a short sword (gladius), a dagger (pugio), a pair of heavy sandals (Caligae), a Sarcina (marching pack), about fourteen days worth of food, a waterskin (bladder for water), cooking equipment, two stakes (Sudes murale) for the construction of palisades, and a shovel or wicker basket.

The Roman soldier underwent especially rigorous training; discipline was the base of the army's success and the soldiers were relentlessly and constantly trained with weapons and especially with drill — forced marches with full load and in tight formation were frequent. Discipline was important and infractions were heavily punished by the centurions. However, honours, rewards and promotions were frequently awarded to legionaries who distinguished themselves in battle or through exemplary service.

At Castra Lafe, the common Miles is expected to play the part of a soldier as fully as possible.  Those with a health or injury issue may be made "veterans" and can participate as much as able.  The miles is expected to follow orders and abide by the orders of his superior officers for the duration of the event.