Fires like that don't necessarily move along the ground. It's usually embers blown by the wind onto the roofs of other houses that are mostly to blame.

That "miracle house" that the media keeps showing had just had the old asphalt shingle roof removed and a metal roof put on. That's what is being credited for saving that house.

In places where wildfires are a problem, building codes frequently make metal or other fire-resistant roofing mandatory.