The story with the Roman DNA was in northwest china rather than coastal china. However the Romans never made it that far east to my knowledge but the tocharians certainly did and their descendents live there today. The tocharians were originally basically giant white people who spoke a WESTERN Aryan language. The language is still spoken but dying I believe. The ancient language was used to record a lot of Buddhist scriptures in antiquity so it's also preserved. There are a ton of tocharians mummies in the region, and they are clearly white people, some of whom have blonde or red hair. There is one female mummy that was 6'6", so a giant for back then. Avg. Roman man was only like 5'5". Their clothes are still preserved too and look very similar to what would have been seen in iron age Celtic or Germanic populations. This is also the region where there are a ton of pyramids that were clearly man made. The Chinese govt is doing what it can to obscure these however, and have even been planting trees on top of them.