In that built-up wood assembly I talked about, framing the eave and gable overhangs takes a lot of time and material. SIPs offer more than insulation. They offer structural help and fast dry-in times too. Since log buildings have no cavity insulation in the walls, they need an insulation boost in the roof to meet model energy codes, and SIPS give the builder more mileage by a healthy margin. The log home industry has a whole gamut of roof structures.
SIPS are compatible with all three.
But if you're considering SIPS, do yourself a favor and talk to a SIP supplier before you commit to roof substructure details. If you're used to using some kind of wood-frame assembly and fiber infill, you probably have timber rafters and purlins spaced closer together than they need to be. Remember, standard thicknesses of SIPS can span 10 or 12 feet. A SIP with the insulation value you need has the strength to do a lot of structural work for you. Of course, the substructure still has to carry the total load.