So here’s how I see it. Jim and Pam are the protagonists. They are essentially “Christians” within the scope of the show. Michael and Dwight are their counterparts. Jim and Pam exhibit, to greater and lesser degrees most, if not all of the classical virtues: humility, charity, kindness, patience, self-control, temperance and diligence. They aren’t perfect characters of course. Pam sleeps with her boyfriend, and in some ways is guilty of one of the “vices” that has been mostly forgotten, acedia, in her willingness to let Roy walk all over her. And perhaps we can see a trace of cruelty in Jim's teasing of Dwight at times, but for the most part it is good-natured.
Dwight and Michael on the other hand are almost like mirror opposites of Jim and Pam. Jim and Pam have a healthy (if strained), respectful, relationship that they both wish could be more. Dwight and Michael have a sniping, sycophantic relationship riddled with power struggles. The vices are present in absurd doses in both of these characters, particularly pride, the prince of vices, and it's twin envy. Of course it is the absurdity of the dose of folly, juxtaposed with the level-headed virtue of Jim and Pam that makes the show so funny.
If we continue pushing this framework we can see that in many cases the less central characters represent particular vices and follies heightened to the level of absurdity and thus humor. Stanley practically is a sloth. Angela is wrath incarnate. Meredith is a big bundle of lust and gluttony (in the form of drunkenness). Oscar is a sodomite. Creed is greed (i.e. theft). Kevin is a male counterpart to Meredith's lust and gluttony. Kelly is a fool (sloth considered mentally perhaps?), and envious/greedy for a life that is not real. Phyllis exemplifies the acedia, or "indolence of the heart" mentioned above, particularly in her relationship to Angela.
Roy presents an interesting case, because while at first he is presented as a picture of wrath his character exhibits key differences from the others. For one thing his vices are much more believable. He is not a caricature of wrath, but rather the kind of spiteful and cruel boyfriend/husband we've all seen or met. Thus he is much easier to despise. Dwight makes us angry, but there is something in his daffiness that makes us laugh and maybe even pity him a bit. Kevin just makes us shake our head. But Roy we really dislike. Roy is an ass. We want Jim to punch him. But then there's the second interesting thing about Roy. He seems to convert when Pam finally confronts him and calls off the wedding. Indeed he's the only one we can imagine converting. The others are too deeply, intrinsically what they are. We can't imagine a Kevin that's not lazy and childish, or an Angela that's not a witch. But Roy, precisely because he is the kind of jerk we recognize from real life, can believably experience redemption. (Although admittedly I'm only in Season 3, so we'll have to see if it takes.)
I think there is much more that could be said, and more that could be traced out on this topic, but I'll leave it hear for now. I think the Office is a great contribution to modern entertainment. It's a program that celebrates the good (who doesn't love Jim and Pam?) and has a good-hearted chuckle at folly. That is as it should be.