My roses develop Rust every year like clock work, and I haven’t been able to eliminate it. They face west and get about nine hours of sun. The affected varieties are Mustard & Ketchup, Radiant Perfume, and Sterling Silver. Any help?
Try increasing the water. Water stress can force, literally, even resistant types to both mildew and rust. It won’t cure every case, in every location, but it may help with some of it. I had read of the water stress induced mildew in rose books and tested the idea. It worked. I accidentally discovered the water stress induced rust by drying out a potted R. Arkansana in spring, forcing the whole thing to rust from top to bottom. I removed the foliage and watered it copiously. It broke out in gorgeous, healthy new foliage. I waited several weeks and deliberately dried it out again and it again rusted. So, to test whether your roses are experiencing water stress induced rust, increase the water and see if it helps. It might, or it might not, but at least you’ll know if that is a factor. Nine hours of western sun can easily induce water stress, particularly if there is hardscape of any kind close to the bushes. I hope it helps. Good luck.
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Thanks for the suggestion!
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The reasoning is sound. I know a grower who irrigates their roses quite generously, and they’ve never had issues with rust. That said, excessive moisture can create ideal conditions for foliar mildew, so there’s a balance to strike. Rose care really is a nuanced dance between hydration and airflow I suppose.
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You wrote “excessive moisture can create ideal conditions for foliar mildew.” I am not sure I agree with that or I am misunderstanding what you mean. One of the ways to prevent powdery mildew is to mist the top of the bushes a few times each day. Mildew conditions, in most regions, are when it’s sunny, dry, and beginning to cool off at night. Around here (Chicagoland) this would be in August/September usually. If you mean blackspot, a blackspot spore needs something like 6 hours of continuous moisture to do its damage. As long as one wets foliage early in the day Blackspot should not result from that. What blackspot loves is a warm, overnight rain. Can’t prevent that 
Thank you very much for your help. I was unaware of this, I’ve always assumed the leaf mildew was due to over moisture at the root level - misting the leaves I assumed would create other issues. Again, I love getting more insight into my rose hobby.