Just be sure your plants are in very well-draining soil mix, have bright light, and that they are not subjected to (prolonged) cold temperatures. That should/would eliminate root problems. Also keep in mind, plumeria that are dormant, or even those that haven't yet begun to grow new leaves and would be considered semi-dormant, don't need much moisture at all. Leaves and transpiration/photosynthesis dictate their need for moisture. That's the reason we don't water those plants that are being rooted. They can't utilize moisture and thus are prone to rot.
