Who are considered to be ancient ancestors of Romans?

From my understanding their was so much intermixing over the years it is hard to tell. Ethnic Romans were descendants of Indo-European Italic peoples and non-Indo-European Mediterranean peoples (myths say they are descended from Trojan refugees from Greece). They began in Italy in an area called Latium. Eventually they expanded their empire to what is now France, Spain, Portugal, the United Kingdom, Germany, and parts of Eastern Europe and the Near East. When they invaded a nation (i.e. the Celtic Gauls in France) they would intermix with them. Gauls and Romans produced Gallo-Romans. Celtiberians in Spain and Romans produced Hispano-Romans. Later, Germanic tribes took over the Western part of Rome and intermixed with the Gallo-Romans, Hispano-Romans, Roman-Romans, etc. producing the French, Spanish, Italian, Portuguese, etc. peoples.

All in all, many European peoples have Roman blood but their exists no pure Roman people in Modern Europe. Romance speaking people probably have more Roman ancestry than a Russian or German for example, but still possess German, Celtic, and even Middle Eastern blood.