Yeah, the whole dynamic of State and Religion is quite interesting. Do you know anything about how much Roman religion interfered in their politics? I think I heard something about it some time ago, but can't remember it.
Now Roman religion is definitely interesting... I would say those in power "abused" the religion for their own (political) needs. That's what pretty much always happened.
It's a polytheistic religion that serves the state. Romans didn't fear their gods, the gods helped them through all sorts of deals. Take sacrifices for example: the gods got the useless stuff no one eats and the rest was distributed to the people who were present at the sacrifice. :) It's a very practical religion. There were even ceremonies where the gods of enemies were allowed into the Roman pantheon.
There also was no canon: you could believe what you want to believe, as long as you follow the correct rituals! There are many different and conflicting myths. I'm sure many Romans didn't believe in all that nonsense. The only thing that matters was following the correct rituals! If you fuck up a ritual that will mean doom for the state!
So, very practical and ritualistic religion. No one would kill you if you said Jupiter didn't exist... As long as you followed all the correct rituals...