Roses are quite amazingly tough and can survive quite a lot of neglect, and you have clearly looked after yours. We get a lot of black spot here in Wales and I have realised that it is best to spray really early in the season, before it gets a chance to get hold, and then repeat spray at regular intervals. Hiowever, even rampant black spot does not seem to kill them, only disfigure and weaken them for that season. I am definitely a learner when it comes to roses. In the past I've avoided them, since we have such a problem with black spot in this wet climate. However, I have learnt that the difference betwen roses thriving and merely surviving lies in feeding them and mulching them really generously.