Interesting.
I dont think I would raise my own without some sort of building to house the cages in. Preferably with at least some climate control.
I raise my own mice, just set up the second cage for the "pets" my wife and kids wanted out of my first or second litter. I find that by cleaning the cages twice weekly the smell is nearly nonexistant, however they are mice not rats.
I read somewhere, on a forum, that if you put a small amount of vanilla extract in the water it causes the mice / rats to smell less. I can not vouch for the safety however, since my first attempt died. (I think it was bad mice, the mommy to be chewed herself apart giving birth, ate the babies, and died from her wound. The daddy, well I havent a clue why he died.. Just to be safe I dont do the Vanilla stuff any more.)