Overview
Roman rule turned Greek dress into a statement. Greece was a province, but Greek culture carried enormous prestige at Rome, and the himation — which Latin called the pallium — became the recognised uniform of the Greek-educated man across the empire. Wearing it in Rome was a claim about learning, and it was read as one.
Key garments and style
The garments barely change: a tunic with the pallium draped over it, the same rectangle of cloth Greeks had worn for centuries, now worn under a Roman administration. What changes is what it signifies. The toga marked the Roman citizen; the pallium marked the Hellene, and later the philosopher specifically, to the point that Roman writers use throwing on a pallium as shorthand for affecting Greek learning. Early Christian writers then adopted the same garment as the dress of their own teachers, which is how Tertullian came to write a whole treatise on it.
Imperial trade brought better materials into the same shapes — silk reaching the Mediterranean through Parthian hands, and improved dyes — so the cloth grew richer while the cut stayed conservative. Roman items did circulate in Greece, and the fastened tunic and the practical cloak appear in provincial contexts, but the draped mantle held the ground that mattered.
Transition
As the empire’s centre of gravity moved east to Constantinople, this dress did not break but evolved: the draped pallium gave way to the cut and sewn tunic, the long-sleeved dalmatic and the fastened cloak of Byzantine costume.