The cultus deorum Romanorum ('cults of the Roman gods') is a collective term for the various cults and rituals which constituted the religious life of Rome until the edict of Theodosius in 390 C.E. barring public cult. The cultus deorum began as the practices of the farmers of the village of Rome.
"I am quite certain that Romulus by instituting auspices, and Numa ritual, laid the foundations of our state, which would never have been able to be so great had not the immortal gods been placated to the utmost extent." -- Cicero "On the Nature of the Gods"
Influenced by their Etruscan, Greek and Phonecian neighbours, the Romans developed a complex state religion that emphasised the patron -client relationship between the gods and Romans: the pax deorum (religio) and maintaining it by scrupulous observance of rituals. 
Variety of cults
Roman religion was embedded in Rome's culture.
It is also difficult to talk about Roman religion as a whole, since it is really composed of a large number of separate cults: there are many Roman religions. It is a ritualistic religion, a social religion that maintained the well-being of the community, a civic religion; the ethical code of the community, the one that prevailed.
The cultus deorum is complex and includes mystery cults that catered to the individual as well as state cults and fraternal collegia.
Religious specialists such as sacerdotes, flamines, pontifices and augures advised magistrates on point of ritual and law.
The paterfamilias in his home and magistrates in public normally performed religious rituals.
Beliefs and attitudes
Romans believed the gods were benevolent and respected the social code of the city. They abhorred superstitio which was a belief that the gods were vengeful, jealous and the attendant excessive and slavish behavior to placate them.
Varro said, "The religious man reveres the Gods as he would his parents, for they are good, more apt to spare than to punish" and "The Gods do not want sacrifice, their statues even less."
A perfunctory performance of a ritual, without any feeling, was simply not acceptable. Even Cicero, known for his cynical attitudes toward religion, speaks to the requirement of mental attitude in approaching the Gods, and that material gifts are less important  .
Cicero also cites the stoic philosopher Q. Lucilius Balbus' opinion about the cultus deorum: "Quos deos et venerari et colere debemus, cultus autem deorum est optumus idemque castissimus atque sanctissimus plenissimusque pietatis, ut eos semper pura integra incorrupta et mente et voce veneremur. Non enim philosophi solum verum etiam maiores nostri superstitionem a religione separaverunt." 
("We must revere and worship the gods, and the best "cultus doerum" is the most sacred, the most holy and the most full of dutifulness, in order to adorn them always with pure, whole and uncorrupted mind and word. Not only the philosophers but also our ancestors divided the superstitio from the religio.")
- ↑ 1.1 1.2 Scheid, John An Introduction to Roman Religion (ISBN 0253343771)
- ↑ 2.1 2.2 2.3 Rupke, Jörg "Religion of the Romans"(ISBN 0745630154)
- ↑ Cicero: De Legibus 2.8.19; 2.10.24
- ↑ Cicero de Natura deorum, II, 71
As practised in Nova Roma
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