We know all that. They weren't Romans at the time, but just a few stragglers from Troy who had a little run-in with Carthage and whose wives had just burned their fleet so it is natural they would be a little testy. At the time of the sack of Rome, there were no Romans in Rome. Everybody else was in Rome; the Romans were elsewhere--still are.
I'm not talking aobut the Aenied -- which was a fairy tale concocted to make Caesar Augustus feel good. At the time of the Sack of Rome in the 4th century B.C., the Romans as we know it were in Rome -- they had thrown out their Etruscan kings in the previous century. Whaddya mean the Romans were elsewhere outside rome?