Since I use a ditch to keep trolls out, I use stone more for decoration or height than for defense.

A normal thatch roof will protect you from drakes. I once had an unexpected drake raid while I was in the area of my very first base. I just went inside and waited for them to leave. You will need a roof over your farm animals though. If you visit the frost caves, your animal shelter will have to be completely enclosed, no windows, no gaps.