Agreed: the details of the burial suggest that the three European-type skeletons were probably long term residents if not necessarily natives. I wrote hastily; what I had in mind was a merchant colony, which could even have been of substantial size and duration. That doesn't rule out a stray "white tribe," but it's a plausible scenario. I am willing to be surprised by this part of the world.
Are there any records of Chinese travellers in Rome or elsewhere in the Mediterranean during ancient times? I would be surprised if there are not, but I don't know the field.