I would add, Don't be intimidated. Roses are pretty rugged plants.
They don't *need* to be fertilized if the soil they're in is good, but every spring & fall you can just apply a 3" layer of compost & water it well. Keep them mulched deeply to avoid weeds & high water bills. Straw, hay, leaves, beauty bark, it's all good. Unless you have slug problems, bury melon rinds & banana peels under the mulch. Watering with reclaimed, soapy/foody kitchen water is great too. Real soap breaks down into great food plants -- the American colonists fed their gardens with wash water containing lard soap.
To avoid disease the best thing you can do is have healthy plants. The more sun, the better, and they like good air circulation, so don't cram a bunch of other plants real close to them. They *can* be moved if their position seems to be challenging them. Ask at a nursery that specializes in roses (not a hardware store garden center).
I've never tried the yogurt solution but it makes sense. I've used a solution of 1 tsp baking soda & a few drops liquid Dr Bronner's soap per quart of water. This has "brought back" roses that were so covered in black spot they'd almost completely defoliated. It supposedly prevents fungal spores from germinating, so also spray the ground around the roses. Use it up to once a week. I find after the plants are fully leafed out in spring I don't need to use it anymore (because the spores never got a chance to establish themselves). If buggies start chewing on my roses I spray them liberally with peppermint or lavender Dr Bronner's in water. A strong garlic tea might work, or a cayenne tea, depending on what the bugs are. (The garlic smell goes away in a day or so). And, you know, don't panic over a few fungal spots or one caterpillar.
Pruning sounds complicated, but give yourself a few years and a book with pictures and you'll achieve a balance. If your roses are short and have fewer, very large, blooms than you'd like, prune less severely next year. If they're tall and floppy with blooms only at the tips, prune more severely next year. Either way you won't kill them. If you have antique roses, that bloom only once in the spring, prune them right after blooming or not at all that year; if you wait till late winter, you won't get any roses in spring.
Rodale Press has very good books on organic gardening & I'm sure they have one or more about roses.