I am not aware of any diseases that lizards would carry and could transfer to snakes that would require you to quarantine them in separate rooms.
Having said that, you should always thoroughly wash your hands or use ample hand sanitizer when moving in between species because there are bacteria that cause upper respiratory infections, mites(?), and salmonella that the individuals may be carrying and not be symptomatic.
In the posts below we were mostly concerned about the mixing of Boas and Pythons. Boas can carry Inclusion Body Disease and be asymptomatic for a long time but still pass it on to Pythons. Very little is known about this disease except that it is slower moving in Boas and is less often fatal in them. So far it has been fast moving and 100% lethal in Ball Pythons, however.
So you could bring an apparently health Boa into your collection only to find it has spread this disease to all of your Ball Pythons, unless you quarantine it for a year or more (in which time you would hope to see symptoms of the disease in the Boa).
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Lincoln, NE
0.1 Pastel, 1.0 Pastel het Pied, 0.1 Pied, 0.1 Cinn, 1.0 Black Pewter, 1.1 Normals, 1.0 Thayeri, 0.1 Thayeri X Alterna, 0.1 crazy cat, 1.0 husband