I remember reading that roofing in medieval England could be very particular to the region/materials available. Some places in Wales, it was common for even poor peasant huts to have slate roof tiles. Transportation (and market) limitations caused more trouble than productive bottlenecks.

Thatched roofs like this are still in use today in some areas! It's actually really good insulation, and eco-friendly. They're awfully flammable though, and they do need more regular maintenance.

Plus birds and bugs tend to like them. Birds I don't mind, but fuck having bugs in one's roof. Give me slate tiling any day, I'll take the cold. :p