Romans were not racists at all and not rated by skin colour. Seneca the Younger claimed that people with black complexion were not a surprise in Rome.
An interesting argument from Seneca is below.
In the next place, we ought to conder the whole state of mankind, in order to pass a just judgment on all the occurrences of life: for it is unjust to blame individuals for a vice which is common to all. The colour of an Æthiop is not remarkable amongs this own people, nor is any man in Germany ashamed of red hair rolled into a knot. You cannot call anything peculiar or disgraceful in a particular man if it is the general characteristic of his nation.
– Seneca the Youher, De Ira, XXVI
The Romans used the general term for black inhabitants, describing them as “Ethiopians”. The Ethiopians had their own state – the Kingdom of Aksum – which in the first century BCE experienced its “golden period”. Goods were transported from the port of Adulis to the Mediterranean, as well as to India and Ceylon. The Romans maintained commercial contact with the Ethiopians. Thanks to the fact that the residents of Aksum certainly had a black skin colour, hence the general term for all black people in the Empire.