Roman helmets were made of iron; the above is style worn by officers. The crest, not as a rule so large as the Greek, was, like it, made of metal, horsehair, or plumes.
Under his armour Roman soldiers wore a rust-red tunica, a little shorter than that of civilians. Above the neckline of metal appears, in the representations of soldiers, a roll of cloth apparently of the same material as the tunica, which might indeed have been an extra, twisted piece designed to protect the neck from chafing.
The lorica or breastplate was of different kinds:
Cast metal. The front and back were hinged and clasped under the arms, and hinged shoulder-pieces clasped onto the front, as we see on General Antinous Pius to the right. Only officers wore this style and frequently not by them, being less comfortable than the other kinds, all of which employed leather jackets, waist-length, as a foundation.
Chain (iron links)
Plates in sections.
This is the armor depicted on the Column of Trajan and is probably the best-known and most easily reproduced. It may be called "articulated "and is seen in various styles. The armor to the right has a widish plate across the chest and one like it in back, and below these, overlapping, five more horizontal plates. Four overlapping plates in graduated sizes form the shoulder-strap.
Any lorica might have, as additional protection, a short petticoat of leather, metal-tipped tabs, descending from the bottom of the lorica to hip or mid-thigh, and the same sort of tabs around the armhole.
Greaves, like those of the Greeks were occasionally, but not often, included in the armor. Bracchae (bracae) -- the word is an ancestor of "breeches" -- were adopted by soldiers for the campaigns in the north, as a concession to the cold.
They were rather like modern "shorts," though sometimes narrower and occasionally longer, always, apparently, long enough to show below the tunica. Romans scorned them as the garb of barbarians, and the legionaries removed them before reentering Rome. Nevertheless, they became more and more popular in the later Empire, and in the next period were an essential part of all men's dress.
On their feet soldiers wore caligulae in various styles, all of open construction and all coming up over the ankle; they were of brown leather. The officer's caligulae were more like the calcaeus.
The Roman shield, made of leather stretched on a metal frame, was oblong, convex, and carried metal decorations, usually the insignia of a man's legion. The sword was short and thick, protected by an ornamental scabbard. Short stocky daggers, worn at the right of the belt, were often included in a soldier's equipment. A sword-belt, when worn, was slung diagonally from shoulder to hip. Roman standards displayed the badges of the companies; the legion standard was topped by a gilt eagle with spread wings, holding a thunderbolt in its claws.
Sources: History of Costume, Historic Costume for the Stage by Lucy Barton