That place in Brazil has both flatter and shallow sloped roofs. Tiled as far as I can see. The buildings themselves seem to be of a timber and stone build then rendered. There's certainly no shortage of lime in our region, although producing it on a large scale may prove expensive in terms of human life. Perhaps we can capture and enslave orcs to do it? Thatching may also be an option in some cases, especially if there are reed beds available. These would likely be steeper. Clay for tiles might have to be brought in from elsewhere.