The Romans were an advanced human society on Earth, with a highly developed culture, that controlled the Roman Empire during the the planet's early centuries. The Romans, and their Empire were centralized in Rome, located in the future nation-state of Italy. The official language of the Romans was known as Latin.
A type of Roman condiment is garum. (TOS: "Bread and Circuses")
Spock's analysis of the degredation of the cultural development of the civilization found on Sigma Draconis VI, was comparable to when the Romans were warring with the barbarians. (TOS: "Spock's Brain")
Julian Bashir owned a holosuite program entitled Roman chariot races, which depicted this classic form of Roman entertainment. (DS9: "Body Parts")
The proverb, "When in Rome...do as the Romans do", often refers to the practice of following suit with what others are doing. (DS9: "Let He Who Is Without Sin..."; ENT: "Babel One")