Actually, a great deal of time is spent examining this issue in the appendices of
Return of the King and especially in the
Silmarillion. Someone else here will certainly be better equipped than I to explain Tolkien's lone god Iluvatar, the angelic Valar and Maiar, the fallen Vala Morgoth and his role as the Great Adversary, and the fate of Elves and Men.
With the possible exception of the Elves, his cosmology is quite Catholic.
Ping post #10.