Answer: Late November is a bit too late to apply fertilizer, as you don't want to have fresh tender growth that is susceptible to frost damage. The same is true for pruning. Major pruning of hybrid roses takes place in January in the low desert, with a lighter pruning again in September. Fertilizing begins in January, with a slow-release application every 6 months up until the heat hits, usually early June. Then stop fertilizing until cool weather starts, usually late September. Fertilize every six weeks until about early to mid-November.
Since I assume you are not here in the summer, I wonder if your roses are receiving sufficient water during that critical time? They could be stressed and therefore not producing much bloom. They need to be watered about 3-4 times per week from June through August, with slow deep waterings that soak about 2 feet deep for mature roses. If you have an automatic drip system, make sure that it runs long enough to provide this moisture during the summer. Use a sharp probe to stick into the soil. It will move easily through wet soil and stop at dry soil.
Black spot is actually not very common in the low desert, usually appearing more in humid climates. This might also be an indication that your roses are under stress. I would get rid of the black spot and dispose of affected leaves. I hope this info helps.
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