Just wanted to point out something : the difference between the Roman Empire and modern Europe makes unlikely that they could have come up with a perception of races similar to what we’ve been accustomed to.
If you take, say 19 century Europe, where racial/racist concept were formally formulated, you have a peculiar situation :
-Europe isn’t merely “more civilized”, which might be subjective, it has an overwhelming, staggering, technical advance, and it has ben so for centuries (in fact, the more time had passed, the more staggering the advance). Any people, country, culture outside Europe can be crushed at will. It’s only an issue of logistics. A millenia old other culture might be submitted with a couple gunboats. In these circumstances, European superiority isn’t a debatable subjective opinion, it’s a blatant, ovious, fact.
-All white Europeans belong to this civilization.
-No non white European culture/country/people does.
In these circumstances, the demarcation line is easy There are white Europeans on one side and everybody else on the other. Feeling that white Europeans belong to a superior race is an easy step to take, and the rest is only a matter of defining other demarcation lines (white/yellow/black) and subjectively grading other cultures/races (mostly according to their technical know how).
However, none of this is true for the Roman Empire.
-Regardless how Roman might have felt that their (and Greek) culture was “superior”, it was an incontroversial fact that a variety of other civilizations were on par with it. They had exactly as big monuments, exactly as much technical know how, exactly as ass kicking armies. If anything, the Romans were the newcomers in this civilization thing, vastly predated by the Egyptians, Mesopotamians, etc… and they knew it and aknowledged it.
-Civilization had obviously nothing to do with ethnicity, let alone with being a white European. Civilized people would come in a a variety of brown shades, including very dark, as in the already mentioned Nubians. If anything, the most obviously uncivilized people Romans would have been familiar with were precisely those pale-skinned, fair-haired Barbarians to the North. And the “center of the world” definitely wasn’t Europe but rather the Eastern Mediterranean, Italy itself being rather on the outskirts of the civilize world.
-Finally, civilized people weren’t overwhelmingly dominating. They might be perceived as having better mores, might have nicer monuments, etc… But the most uncivilized people around, regardless again of skin shade could (and would) kick the ass of Roman legions if given the chance. Romans didn’t have the luxury of thinking of themselves as invincible, as 19th century Europeans would. They were acutely aware that at any time someone else, civilized or uncivilized, darker skinned or fairer skinned, could crush their armies, ravage their land, pillage their cities and sell them into slavery.
So, it makes no sense to project late European views of races unto the Roman. Making the assumption that somehow they would perceive races the way we do is IMO making an extraordinary claim that would require to be supported by significant evidences, not the other way around.
Doubly so because our concept of race is, franckly, counter-intuitive. I’m perfectly aware that most people currently have a hard time with the seemingly modern concept that there aren’t no races. Stating so will make many people think that you’re just in denial of reality. But reality is in fact on the side of the absence of races and the belief that there are such things is completely cultural (if deeply ingrained) and has to rely on a variety of, again, objectively counter-intuitive intellectual contortions. Not the thread to give a lecture on this topic, but for instance, you need to ignore that southern Indians can be as much or more dark skinned than Africans, to ignore the obvious continuum nature of skin colour, to decide that the current American president is “black” despite him being genetically exactly as much African as European, and raised by white-skinned people to boot, to brand “white” an Anwar el Sadate decidedly darker than a “black” Haile Selassie, etc…
Again, assuming that ancient Romans (or members of others Mediterranean cultures, like say, those often mentioned Egyptians) would have somehow come up with the same kind of intellectual contortions, especially in the absence of comparable historical circumstances is something that would require serious evidences to be worth arguing about.