Hatchlings Kept Together?

[Alicia]

Nope. They cannot be housed together. Period.

Not only must all new snakes be quarantined as far away from each other as practical, rosy boas and ball pythons have vastly different needs. Your rosy will benefit from the lower humidity of a screen-topped tank (in fact, it's okay if her temps are a little lower, as well -- an 80 degree cool side is a bit much for a rosy). Rosy boas, of course, do poorly with high humidity. Lower is better for them. Your ball python, meanwhile, will require humidity that is higher and more consistent than a screen-top can provide -- a tub with an under tank heater on a thermostat is an awesome setup for a BP.

If that wasn't enough of a reason, odds are incredibly good that the rosy boa will attempt to bite and constrict the BP around feeding time, or whenever she thinks it's feeding time. Unless something is wrong, or it's slowing down for winter, a rosy tends to think with its stomach.

Even if they weren't such different species with different needs, quarantine is still a must. Ideally, in a different part of the house, for a bare minimum of two months. Don't want anyone getting mites or worse, right?