That’s a lot of snakes! All I know about rat snakes is that they can get through about anything except for hardware cloth (HWC). Put it everywhere you can and bury it around the perimeter if possible.
This will sound crazy, but does your coop have a corrugated metal roof? Years ago, I had one getting into my chicken tractor by going through the dern roof corrugations. I block those off now.
Failing all of that, kill ’em all. At least they’re coming to you.
You are killing them, right? Just asking because if you’re just turning them loose down the road a piece, you’re getting repeat business.