I have had roses improve in this regard with time, although many still get it in the fall. It's just the nature of the beast in my wet, humid climate. Some also get it after their first flush unless I fertilize. All that blooming takes it out of them. However, some defoliate regardless and haven't improved, but those usually defoliate as soon as they can! I think there's hope for improvement, but I wouldn't be upset if they just got BS in the fall when things tend to wind down.

edanz, in general, a fully developed rose will have better disease resistance than its baby version, and that's why people often don't judge a rose when it's not fully developed.

I don't have blackspot in my area but powder mildew is very popular. In the first two years, my Scepter'd Isle (bare root grafted on Dr Huey) had powdery mildew all the time. However, from the third year and after, it's almost carefree.

Roses also easily have diseases when they are under stress (not enough water, too much water, not enough sun, not enough nutrition, not enough air flow...), remove anything that causes stresses to your roses will help them deal with diseases better. Helen

It depends on the disease, and a few other factors. Since powdery mildew is affected by how well hydrated the rose is, which is affected by how well developed the root system is, roses can outgrow it.

Blackspot is a different beast. IME, blackspot resistance doesn't improve over time. It can get worse as the spores 'find' your garden. Also, a lot of nurseries in blackspot prone areas spray with systemic fungicides, and the total effect of those may take a while to wear off.

Try keeping them well fertilized and see what happens. Otherwise one of the things that has been said in the past is that if a rose isn't deemed disease free or disease immune then the implication is that you will see at least some fungal presence - it's like the starting point is "hopelessly susceptible" so that a variety can be well over at the far end of the scale and still be affected to some extent.

Another involved factor is that rose disease fungi have been reported to mutate frequently and rapidly, resulting in variations in what strains are present from one locale to the next. So it might be that the Austin disease resistance depictions are based primarily, if not entirely on what has been seen on their own growing grounds. With for instance their black spot not being the same as your possibly more virulent black spot.

I also find it depends on the individual plant and your garden micro-climate as well. I have grown Peace for example in different sides of the garden three times and my experience have been vastly different. My first plant was grief stricken with black spots, while the second was stunted. My third plant was so robust and didn't have black spot on her. Unfortunately I lost her during the polar vortex a few years back.