[bumbada]

are we to consider them a continuation of the Roman civilization?

Yes, because being Roman had nothing to do with ethnicity. Even people from Italy were not Romans at first. The Latins people allies of Romans(socii) fought wars to be recognized as fully Romans and only after winning some battles they got it.

In Jesus time only 10% of the population had Roman citizenship, like St Paul, but after some centuries everyone had it.

Something similar happened in the US, black people were certainly not fully Americans or even people at first, they were slaves, let alone native Americans, devoid of any right.

The survivors that were not exterminated(like native Americans) fought for their rights and eventually they got it, after having lots of their houses burned,their women raped and their men murdered. They were sent to World wars in the worst conditions at the most risky positions.

Rome was a way of living, way beyond ethnicity. You only understand it when you travel to places without this heritage, like China or Afghanistan.

When I traveled to China I was surprised to live in a place with no rule of law for example. The Rule is whatever the CCP leaders want today. I took so many things from the West for granted.