Septimius Severus and other Black Romans.
Not very many people seem to realise that one of the Roman Emperors was Black - Septimius Severus, who was one of the four ruling Roman Emperors to come to Britain (they were Claudius, Septimius Severus, Constantius Chlorus, who died at York, and Constantine, his son, who was declared emperor at York). Hadrian came to Britain but wasn't emperor at the time. You never see depictions of Black Romans. There were also Syrians, and people from all over the Roman Empire. There's a brilliant book which emphasises this: The Emperor's Babe by Bernadine Evaristo.