。
The wall was made of rough stone.
Literal
Wall [topic-は] rough stone [with-で] made was.
ざらざら is a 擬態語 (state mimetic) for rough, grainy, sandpaper-like texture. ざらざらとした石 uses the mimetic as an adjective via と + した. 出来ていた is the past resulting state of 出来る (to be made of).