Fall is a time of transition for the rose garden. Your roses are slowing down and preparing to go into dormancy. Now is the time to take a break from fretting about insect damage and disease and to allow the coming winter weather solve most of your problems.
After a long hot, humid, rainy or dry summer your roses will surely be looking a little rough around the edges. Come fall even the best kept roses can be showing signs of insect damage, fungi infestation or just general raggedness. The best thing you can do is not overreact and recognize your roses are simply ready for their winter break.
I have assisted many stressed gardeners, who've stopped by their local Master Garden office during the fall. The biggest fall issues encountered aren't the diseases themselves, but simply tired plants. With the colder weather and dormant period shortly arriving an amazing amount of these issues will take care of themselves. Treating most problems your roses have in the fall by spraying or dusting can actually cause more stress to the plants than if they are simply left alone.
This doesn't mean you should forget your roses in the fall. You should always remove leaves and canes heavily infested with fungi or disease. You'll also want to prune away any dead, diseased or rubbing canes. Try not to disturb your roses otherwise. Allow them to develop their rose hips which will help them settle into fall and also stop fertilizing to prepare your roses for winter rest.
Fall is the time to clean up your flower beds. The frequency of disease can be reduced by removing all of your old mulch and replacing it with fresh. This doesn't need to be done with all of your flower beds just the areas around your roses. You wouldn't believe how many nasty fungi, diseases and insects can overwinter in your mulch only to reemerge next spring.
Enjoy your fall weather, clean up your flower beds and start making your gardening plans for the spring. Ignore the insect and fungal damage that isn't covering the majority of your rose bushes. Your roses will appreciate not being stressed by unnecessary chemicals and you'll benefit from enjoying the garden while mother nature does her job.