Polytheism

I'm not sure if this is the right area to ask but is there any S.I.G. On polytheism?

That all depends on which form of polytheism you are referring to. The most appropriate would be the Paganism section and you are welcome to post any thoughts and discussions there.

What would the hougts of ancient roman and greek gods fall under or what similar topic would this be? Or is this also in the pagan beliefs

I would probably put it in the pagan section. This definition comes from Wikipedia:

"Paganism (from Latin paganus, meaning "country dweller", "rustic") is a blanket term, typically used to refer to religious traditions which are polytheistic or indigenous.
It is primarily used in a historical context, referring to Greco-Roman polytheism as well as the polytheistic traditions of Europe and North Africa before Christianization. In a wider sense, extended to contemporary religions, it includes most of the Eastern religions and the indigenous traditions of the Americas, Central Asia, Australia and Africa; as well as non-Abrahamic folk religion in general."

Feel free to post your thoughts, insights and discussion points there and let me know if you need any assistance