This Spring, I bought several of the Generosa and Renaissance series roses which were sold at K-Mart through their Martha Stewart marketing. Some of this I got for bargain prices--as low as $4. I have been impressed by the resistance of these roses to blackspot. I haven't seen any on these roses yet, and the weather conditions have been very favorable (hot and humid). In contrast, the hybrid tea roses in our garden have been devastated by black spot.
This was the first year I learned my lesson and am now focusing on roses that are truly resistant to fungal diseases. Some others that are performing really well for me: Duchesse d'Brabant (Tea Rose), La Biche (Noisette), Nearly Wild, La Marne (polyantha, and Louis Philippe (China). I have not been as impressed by an old garden rose called 'Martha Gonzalez.' It's a great looking rose but has had blackspot problems for me here in North-Central Alabama.
I have three of the Generosas and all of the Renaissance Roses. Sonia Rykiel has very minor blackspot, but had a big problem with rust last year, Elaine Gillet and Florence are clean. Many of my Ren roses had powdery mildew, sort of surprized me, and Isabel has a horrible case of BS, nearly defoliated, going to strip the remaining leaves and let it start all over. Ones that had PM, in order of seriousness, Clair, Bella, Julia & Helena. Prinny Alex looks good and clean, but rather HTish. Sophia is looking great and just bloomed, I think its going to be my favourite, blooms are just lovely and very double, it can easily compete with the Austins for beauty. This is first year for them all though, so its unfair to judge them until their better established, I have high hopes for them!
I did the same thing as you did by purchasing lots of these roses at K-Mart. I was bitten by the bug a little earlier tho' and had to shell out full price for them. I live in Zone 4 and am delighted with the performance of these roses. Not a single bit of blackspot or disease on any of them, I purchased eight different varieties and my favorite so far is Paul Bucose, continuous bloom and is extremely gragrant. Sonia is a little top heavy and not as prolific as I would have liked. Isabel renassaince is outstanding for color and fragrance. A deep black red with thick canes and great perfume. Martine Guilliot is a little late, but also magnificent. My other shrub roses and Hybrid T's have finished thier first flushes and are waiting for new bud growth, but my K-Mart roses have never stopped. I am very impressed with these and will be watching for new varieties next spring as well. Worth every penny. Wish I could have picked up some bargains like you did...our K-Marts here did discount them 30% of and I did purchase 2 more...but maybe I'll watch this week and see if there is a further reduction. I was there the other day and they only had a few left and none of them were tagged...but they didn't look too bad for sitting in the parking lot with very little attention to watering, while thier hybrid t's were quickly defolliating. Nice to know there are other gardeners raving about these roses. Good Luck to you, Kathy