Are all white people able to trace their history back to the roman empire? What about the Greeks? Or were there other white civilizations besides them who most white people can trace back to?
The simple answer is no. For instance, we know there were settlements of Scotland over 8,000 or more years ago, particularly in the Northern Islands. Think of all of the territory above Hadrian's wall and the Roman exit from Britain in late antiquity.
I mean, over time it is likely that someone of that "highlander" ancestry married someone from England or Europe who had some sort of Roman ancestry, but this is not the same as some Italians being the "descendants" of Romans