Simple log cabins, here in the western U.S. usually had split Western Cedar shingles as the final covering on the roof. These would have been built during a time when no insulation was though of since they were often in mountains that would have been inaccessible during winter anyway. The roof construction was sturdy enough, being made of logs that tied the oppoaite walls together called joists and then the "peak" roof, also made of smaller logs that supported a structure of boards sufficient to support the aforesaid shingles. The "pitch" of the roof was often pretty steep, being about 8/12 or even 12/12 so as to shed snow more easily.
The shingles were adequate and being cedar were fairly weather resistant. Problem inherent in cedar shigles is they are not fire resistant and one needed to consider the placement of the cabin... whether it was netled in the woods or in a more open place.
We have nearby cabins here that are in excess of 100 years old. Most required replacement of the bottom row of logs since they rotted out from the groud moisture over the years...