My house is 213 years old. Think I need to do anything yet?
Sorry, but something was lost in the the translation with your Italian friend. There is no way-- none-- with any building material-- any-- that a roof from the 5th century, or the 9th, or the 12th even, could still be intact. Garbage. That would be a miracle material, of some alien technology that has been lost to the ages. In the 5th century, you didn't even have a solid roof on just about anything that wasn't a church or government building! You would be replacing rotting, insect-infested thatching every year. You could have a roof made of solid stone, but it would not be totally water-tight so you'd have to seal it with something that was, in turn, subject to breakdown.
He showed you a bunch of very, very old buildings that have been, by the evidence of their very existence, well maintained-- and that includes patching and eventually replacing their roofs.