In his day, Napoleon Bonaparte said Africa began at the Pyrenees.
Considering Carthage controlled most of southern Spain below the Ebro river until Hannibal conquered the land north of it on his way to Italy, and then based out of southern Italy for the majority of the time he was campaigning there, it really shouldn't be any surprise you'd have a number of africans in ancient rome. Julius Caesar's 8, 9, and 10th (his favorite) legions came from Spain.
Anytime you're talking about Mediterranean civilizations in the ancient world you can rest assured Africans were involved.