It's going to take a book or two for me to address these issues, so let me get straight to whats on my mind today: misbelief about Roman religion. Here are some major myths about Roman religion:
- It was a religion without dogma;
- It was without teachers and teachings;
- It was uncreative or unoriginal, or that the Romans were uncreative or unoriginal in adopting Greek gods;
- Romans were dispassionate about religion;
- Romans were not particularly dedicated to their beliefs, as evidenced by their adopting of Greek gods and later conversion to Christianity.
These myths are untrue, absolutely. They have been perpetuated in our culture through books, theatre, movies, traditions, etc., which is no doubt the result of western civilization having strong Judeo-Christian roots. Modern pop culture has taken it a step further and portrayed Roman civic life as highly immoral, especially where it comes to human sexuality and respect for the dignity of others.
Religion permeated all aspects of Roman life, from civic to private. Each household had gods, and there was an official organized state religion. Even in the Republican and Imperial periods, where there was a strict belief in the separation of church and state, senators considered augury and divination, both central to Roman religion, were crucial elements of the republic. The belief in gods was a ubiquitous phenomena that even the most stoic philosophers took for granted.
However, the mythologies of the gods -- their fantastic stories, loves, rages, jealousies, and sometimes pettiness, were broadly considered by the well-educated civic populations to be artistic creations of the poets (Virgil, Ovid, and Homer for example), and lead to "superstitious" beliefs and practices.
The Roman elite, including the Roman religious officials, considered superstition to be a dangerous force. They would apply this rationale equally to someone blaming Zeus for throwing a lightning bolt at their house as someone claiming to be a god or demigod, which was the case when the Christians arrived on the scene (or in this case, they knew someone who knew someone who was the son of God).
To call the Romans "unimaginative" because they adopted the Greek mythologies as their own is to misunderstand how religions evolve over time, and the role that mythologies play in religion. All religions have mythologies that reinforce the principles of the religion and the world view or the culture. Roman belief systems were a synchretic blend of Hellenistic beliefs and other pre-existing belief systems on the Italian peninsula. A careful examination of Roman mythologies reveals it is extraordinarily different from Greek mythology. Indeed, one can argue that if it weren't for the fact that the early Italian civilizations found parallels to their indigenous gods in the Hellenistic ones that Greek stories may never have become associated with the later Roman empire.
The Romans had no doubt that the gods existed, but they argued widely about the nature of the gods. Some argued that the gods were manifestations of virtues, others that they were ethereal beings without interest in earthly affairs. Others even that they were human creations overlaying a cosmic reality of some divine power.
In any case, it was considered a major civic and individual obligation to show respect for the divine. It was widely believed that to neglect religious obligations could result in the collapse of society. It's not a coincidence that Roman archaeological collections are literally filled with artwork commemorating the divine, and that public temples are one of the most enduring of the empire's archaeological survivors. It is not a coincidence that the highest ranking citizens in Roman life were leaders of the church (the emperor himself was considered the highest ranking religious official, much like how in the United States the president is considered the highest ranking military official.).
Perhaps the most important of all rituals was the maintenance of the eternal flame in Rome. This was entrusted to the Vestal Virgins. Tradition had it that this was, in fact, the ritual of all rituals -- that if the flame was not maintained and annually renewed, that Rome would cease to exist as they knew it.
Extinguishing that flame, and keeping it out, was one of the most important acts of the Christian emperors.
Suggested Reading: Cicero's On the Nature of the Gods (De Natura Deorum), published in 43 BC. He outlines the major religious schools of thought, but doesn't go into the ritual aspects of religious belief.