Building a natural stone machine shet

Hello, I am new to the forum and hope to gain some advise on my plans to build a stone machine shed on my acreage. I have tons of round river stone on my property. It is about twice the size of a softball, and generally oval in shape. I realize this is not the best material for stone work, but it is free. I was thinking of using 4x4 treated posts to support the roof of the machine shed, which I will build using 2x6 and an inexpensive metal roofing material. I would like to build the walls of the shed with the stone I have in abundance on the property. It would not support any weight other than itself, as the posts will support the roof. I was also planning to dig and put cinder block under the stone masonry as a foundation. My question is, do I have to put some sort of material between the stone masonry and the 4x4 treated posts? I have heard that moisture builds up due to temperature differential, but since the stone and wood are side by side, it didn't seem to me like there would be moisture build up.