T.R. Glover's The Conflict of Religion in the Early Roman Empire is a lengthy examination of the various emperors' relationships with religious matters across the Roman Empire during the 1st and 2nd centuries A.D. through the reign of Tertullian, who died in 220 A.D. Of course, most of it deals with the relationship between Rome and Christianity, which was certainly tempestuous until Constantine the Great converted the empire in the early 4th century A.D., but this work also looks closely at Roman mythology and religion as well.