Scriptural evidence for the role and compatibility of polytheism within Buddhism?
Is polytheism dharmic or adharmic? Dhammic
If it is dharmic, what is its role within Buddhism? Different level of consciousness leads to different rebirth.
If it is adharmic, why is this the case? NA
What is the scriptural basis for your answer? There are many suttas with the Buddha encountering Deva (Gods) in Samyutta Nikaya, such as in the Devata Samyutta and the Brahma Samyutta etc.
Also refer to the popular blog about the 31 planes of existence.