Originally Posted by pixi666
What about Eastern light cavalry, like the famed Parthian horse archers? Were their techniques ever used by the Romans?
By Persian-style, I meant anything used/developed specifically by the Persians, like the cataphracts you mentioned.
Horse-archers certainly rode in Roman armies, but they are very poorly documented, especially before the 4th Century. Small numbers of Parthians and Armenians fighting in their native styles (a combination of cataphracts and horse-archers) found their way into Roman armies as mercenaries, allies, and perhaps auxiliaries.
During times of political upheaval (namely the 1st Century BCE and the 3rd Century CE) Rome and Parthia/Persia did occasionally "swap" units of soldiers, so it wasn't impossible to find horse-archers riding under the eagles and legionaries marching under Zoroastrian banners.
Papyri found in Egypt attest to units of horse-archers performing garrison duties in the Nile region during the reign of Diocletian. Whether these were regular soldiers or irregulars of Persian or Arab origin is unknown.
Horse archers may have appeared in the armies of Rome's Eastern client states, but these states seem to have preferred a combination of Arab, Hellenistic, and Roman troop types rather than those of Central Asia. I'm not sure if they are attested for Palmyra, for instance. Parthian horse archers under the command of Zamaris, a Babylonian Jew, are attested in the army of Herod the Great.
By the 5th Century Rome had many horse-archers and these were diverse in origins. Many in the West were renegade Huns and Sarmatians, including elements of Aetius' cavalry. Belisarius had plenty of horse-archers, as I recall.