That was 20 years ago. Now they have to be depicted in any and all characters. So on Brittania, half the Roman Centurions are nubian blacks. Not slaves, centurions. Like the Romans were known for elevating southern africans into full social status with themselves. With some of the Gauls maybe, but the BLACKS?
Anyway, to reality, in 43 BC, the only centurions in the Roman army were Roman citizens, Italics or at best Etruscans. No Gauls, no Phoenicians, no Nubians.
By 300 AD that would change and you could have Nubians who became citiznes under Caracalla's policy