Like most of Europe back then, tile roofs cost money. If you had none you used what was around, which in Italy could be reeds, rye stalks, or even stone (resulting in round buildings that looked like large beehives). Northern Italy was fairly well-blessed with all these materials.
This photo is from a town in Trentino c.1914. The buildings closer to the castle are tiled, while the ones nearer to the photographer are thatched with rye stalks over branches.

Walls are Mediterranean flat bricks and/or local stone, which were usually rendered. The newer 'posh houses' at the back look to have quite 'square' corners, while the nearer ones are a bit more haphazard. That being said, even high-quality dwellings go out of square and plumb over time, as successive layers of rendering and repairs cause walls to look like they are bulging out.
As John says, not everyone had rendered walls either, so rough bare stone dwellings will also work for low-status buildings out in the sticks.
Thanks to those offering links to manufacturers btw! It's always good to have a variety to choose from. I don't suppose Italy is very different to Spain, in that almost every old building is uniquely different to the next and having two or more the same looks wrong unless you spread them out a bit.