I'm glad the rat snake has his own place now. The thing about snakes is that they aren't logical about what size food they can eat, plus most rely on scent rather than anything visual...meaning, if there is the scent of prey on a snake, the room-mate may very well kill & try to eat him, even if it's physically impossible, & the snake will be just as dead. So many ways things can go wrong quickly if cohabbing snakes- even just breeding snakes has risks. Predators will be predators.
There's also the issue of quarantine- each snake could be carrying germs they are okay with, but a snake from another area (or continent) might succumb to.
Certainly various snakes may cross paths in nature, but that's a far cry from captivity, with so little space.