I don't remember seeing this topic when it was up last year, so thanks for bumping it. It's a good conversation to have, since I know a lot of us try to be environmentally conscious and more and more are gardening.
I compost all of my rat litter, as well as food and garden waste. I use this compost on my food garden, which provides most of the produce my husband and I (as well as our rats) eat. We've never been made sick from anything in the garden, and I'm the type of person who will grab a tomato off the vine with dirt-crusted hands and chow down. I know that's anecdotal data, but I'll say that in the few years we've been gardening, we've both gotten food poisoning from restaurants multiple times, so it certainly isn't due to amazing immune systems.
Carnivore manure isn't recommended for composting/gardening for a few reasons. Disease risk was mentioned, but it can also be too "hot" - having too much nitrogen, which can kill plants. Rats, who eat a mostly plant-based diet and have longer intestines, don't have very "hot" manure. [I'm using silly quotes to be clear: this doesn't refer to temperature, but nutrient content.] Cat litter is usually heavy clay, something gardeners fight to keep out of their soil, while most rat litter is wood or paper (I use aspen, in part because I know it composts well). Herbivore manure - cow, horse, goat, rabbit - is like gold on a farm or garden. Many gardeners especially love rabbit waste because it comes mixed with bedding and therefore is even less "hot", meaning it can be applied to plants sooner, and some people even use it uncomposted.
Manure of any sort that is fully composted isn't a disease risk as the composting process will kill pathogens. However, using compost that isn't "mature" can spread disease onto your plants, and should be avoided. I don't put out compost that's been on the pile less than six months, or in which I can identify the original ingredients - it should look like dark, rich soil and not like what you put in.
When I had a dog, I composted his droppings separately, under my ornamental hedges. Even though he was the only member of the family who never ate from the garden, I felt safer keeping his waste out of the compost that was destined to grow our dinners.
A couple other random thoughts... Many pharmaceuticals pass through the body intact. I compost my rats' waste in any case, but it might be a good idea to discontinue doing it while you have a rat on antibiotics - microbiology is so important in compost, so adding microbe-poison could throw off the balance. Also, wild rodents nest in my compost pile. I keep their life cycle in mind and turn my pile in seasons when they don't have eepers, but don't consider them when I'm composting rat waste - since they're closely related species, my colony may well pass diseases to the mice and voles. My answer to that is to keep my guys as healthy as possible, and let the wildlings worry about themselves, but others may feel differently.
Sorry to ramble so much. Obviously, I found the topic interesting