The term 'Roman Soldier' refers to two distinct roles in the Roman military: the Centurion and the Legionary. The Centurion was a professional officer in the Roman army who commanded a unit of 80 to 100 men known as a century. The Legionary was a soldier in the Roman army who served in a legion, which was a large unit of up to 5, 000 men. Both the Centurion and the Legionary were essential to the success of the Roman military.