While there are a number of factors that make a clear picture impossible, consider that there would have been merchants and their representatives flooding in from all over the Empire to make a quick buck in the new provincial capital.https://twitter.com/JackBMontgomery/status/997382346260340736 …
But the idea that trade in goods means mass movement of people is false. Setting up a supply chain in the Roman period wouldn’t have involved mass migration any more than Japanese cars being manufactured in Sunderland means they have a large Japanese pop