If you find yourself needing to dress like a Roman soldier, it’s likely you’re looking for a standard version of roman soldier armor. Nevertheless, don’t worry if you cannot get everything perfect, as roman soldiers didn’t have an official uniform and would have modified what they were wearing based on combat situations. There are some components you won’t want to miss, so always do some research on Ancient Rome’s military outfits.
Even before you consider armor choices, you’re going to need the basics: a tunic and sandals. A tunic is essentially an upside-down sack with head and arm holes. Sometimes they have short sleeves, but they were not a necessary. In Hollywood movies, these are almost always dyed red, but they could also have been left their natural color. The sandals were only really standardized during the time of Imperial Rome, so any sandal that is practical, durable, and leather-based would likely work for a costume.
Next, the Roman soldiers would have had a linen or wool scarf, to absorb sweat and protect their necks from their armor, and wool shorts that went to the knee. They would also have a belt, with dangling straps on the front (called baltea), that would reflect their status. You can add some leather bracers to your Roman costume, but there is almost no historical evidence pointing to their existence in ancient Rome.
On top of the tunic, the Roman soldier would usually have armor. The most iconic armor would be the overlapping metal or leather plates that protect the torso. As with the other elements, the armor generally reflected the financial standing of the soldier. If your costume is meant to be a regular foot-soldier, there should not be a lot of fancy embellishments. Many different designs have historical justifications, and chain mail was fairly common under imperial rule. In addition to the torso, soldiers would typically have a helmet, sometimes with cheek guards and/or a horse-hair plume on top. Styles vary based on time period, but the most well know have a skull-cap, brow ridge, and rear neck protector.
The final touches on a Roman soldier costume would be the shield and weapons. A Roman shield would be curved, to deflect thrusts and projectiles, and extend from shoulder to knee. Although mostly wood, it should have a metal knob in the middle for offensive use. The sword, called a gladius, was relatively short and carried on the right side via a horizontal over-the-shoulder strap. If desired, you can also outfit your costume with a javelin, but keep in mind the situations you will be in.