There's lots of argument on who the Rhodoks are really based on, but I like to think they are loosely based, at least by name, on the island of Rhodes, which is in Greece but was obviously under Roman rule in the previous generations. In the medieval transition period (between Byzantine era and high medieval), it was one of the most important trading posts, and was the base for the Knights Hospitaller during the Crusades, and a station for Byzantine armies in the generations before. It was an important trade and military location until the end of the medieval era because it was a gateway port between southern Europe (Greece, Italy, Spain) and the Middle East.
They were known for their spearmen (Peltasts, of Byzantine discipline), and employed Varangians from an old agreement with the Kievan Rus, and other foreign mercenaries.
In short, the Rhodoks are probably Byzantine+Holy Roman Imperial in influence (crossbows were used by the Crusaders, but not popular among the Byzantine armies).
I want to think that the translated army of the Rhodoks have little/no cavalry to speak of despite the Byzantine/Komnenian doctrine of using heavy cataphract cavalry is because of the mountain topography. This same mountain topography is also why we have a mixed Scottish highlander set of troops in Floris, which I don't object to despite the strange possibility of a Doge mac Domangairt or some other Scottish name.