what countries people are of roman (empire) descent exactly?

Wherever the Romans went outside of Italy they encountered native peoples, many of them hostile, which helps explains all the fighting, doesn't it? What they left behind is mostly culture, language and marble ruins. It's not logical to assume a few Roman cities, garrisons or settlements outside of the Roman homeland were able to transform the DNA of millions of native people i.e. the rest of Europe which was heavily dominated by Germanic tribes. Modern people may fancy they have "Roman blood" but the reality is probably very much different.

The various tribes of europe usurped the original romans so the closest would be germany.