Roman racism was very different from what we'd call racism today. In fact, I wouldn't even call it racism as much as it was cultural exceptionalism. Barring very few exceptions - Persia, Greece, and Ethiopia - the Romans didn't so much as see themselves as a superior race as much as they were a superior culture. The Latins were the original Romans, yes, and the root of the Roman state and identity, but anyone could assimilate into Roman culture and become, well, Roman. Those who did automatically shared in Rome's superiority, no matter their actual ethnicity. In Roman eyes, an African Roman was superior to a German regardless of the latter's closer ethnicity to the Latins/Italians.
Simply put, civis romanus sum. It doesn't matter where you originally came from in the Empire, a Roman citizen is a Roman citizen, and any foreigner that messes with one gets a gladius to the face.