Yep, ratsnakes can be a pain in the coop, for sure. I don't kill them either; I catch them and release them (I've handled snakes most of my life :0) )
Anyhoo, I certainly don't mind ratsnakes around, but I DO mind them eating up my eggs and critters, SO really the best thing to do is snake-proof your coop. They can squeeze into unbelievably tiny openings. We are going to build a new coop and I'm covering everything in 1/4" hardware cloth to keep 'em out. I'm going to plug every single dadgum hole! My current coop is made of tin and they squeeze into this little opening where the tin overlaps. Very annoying! I pretty much have discovered that a good coop is really just a ventilated cube! You really need protection on all six 'sides', floor included.
:0)