I personally would not rush to separate him from the rest of the collection (especially if you have a dedicated reptile room and can't recreate the environment successfully in another room, you don't want to expose a sick animal to inadequate conditions). I've heard a very experienced herp vet say that most typical respiratory infections in snakes are caused by opportunistic bacteria that are already present in our snakes and are not typically contagious. When the immune system is suppressed in any way it can allow the bacteria to become a pathogen, that's when your snake will come down with an RI.
I.E The bacteria causing the RI is most likely present in your other snakes too, it just hasn't been given the chance to become a pathogen. So I don't think your other snakes are at risk by being in the same room.
The only thing I would do is bump up the temps until you can get him into the vet. I believe too much humidity can loosen things up and potentially make them worse.