As for sealing the edge of the roof, the bottom line is that with the exception of fully steel frames homes, the gutter is generally attached directly to the barge boards which are usually timber. So embers fall in gutters, leaves ignite and off you go.
Another thing many people do not realise is that the radiant heat can cause window furnishings to ignite inside the glass; on top of this, flying embers etc in 80-100km/h winds break the glass, and once an ember enters the house it is gone - hence the need for fire shutters, using a similar principal cyclone screens (but solid not mesh)
