The nation formation began in 18 century after french revolution. Ask any italian about his roots, in general every nation beginning a counting from that period.

Italian here. Our roots are at the ancient Roman times, when Italy became for the first time a political entity (in that sense, Augustus' iuramentum to Italy is often quoted to show this); and people claiming otherwise, Italian or not, have a superficial view on Italian history. Even the name "Risorgimento" to indicate the process of Italian unification literally refers to the action of "rising again", with Italian patriots seeing the Italia Romana as the first time they ever rose and the Italian (re)unification as them reclaiming their land. The general idea that most nations were only formed after the French Revolution is an oversimplification that does not take into account the sense of belonging that existed even before the modern concept of nation existed (this goes not just for Italy but for many other European nations as well).

I don't know why your Italian colleague is laughing, assuming this person even exists, but I'd recommend them to return studying history. I understand that most people in school consider it only a succession of events and dates, but if you go beyond that you'll see that it's quite interesting. Same goes for you who gave an extremely superficial description of Romanian history by simply describing it a succession of dominations, whilst assuming that those are always sufficient to completely shift the ethnicity and culture of autoctones, which, in the case of Romania, did not happen, and it's not even a outlier on that sense. If you have such a simplicitatis view on how civilizations and peoples work, what cultural and genetic assimilation is, and in general have bare bones knowledge about Romanian history, then why do you continue insisting on telling other they are wrong when you clearly lack any knowledge to do so?