Holy Roller is a put down term to Christians. This song appears to be directed at evangelists that don’t practice what they preach.
The political influence of the “religious right” in American politics is frequently attempted to be measured. It is also a debate among Christians themselves whether to even engage in politics, as that focuses on Earthly concerns when the focus may better be placed on getting to Heaven.
Scottish hard rockers Nazareth, perhaps sometimes mistaken for a Christian band given their name, released this single in 1975.