Look for works by Robert Garland. He’s done considerable research on the topic of Mediterranean Civilisations that followed the Bronze Age collapse. Religion was an important facet of it. I recommend Greece and Rome: as integrated History link: https://archive.org/details/mbid-c2fb0ad6-d99a-487b-b480-c7267d63013a Though I must say the paperback is hard to find and I myself had to work with an Audiobook. Peter Brown and Ramsay Mcmullan have also produced considerable literature on the development of Roman religion. Just search for their papers on jstor. Hope this helps and best of luck.