Question
How far down would I need to cut back my knockout rose bushes before the winter?  I have had these rose bushes for about 5 years now and this past spring they did not done as well as they usually have in the years past.  Should I leave them the way they are or cut them down a little to get a better stock for next spring?

Answer
As I don't know where you garden, I will have to assume that you get a cold winter. If your roses didn't do well this year, then I would wait until the spring to cut them back. This way if there is a nasty col snap in the winter, the roses will have long enough canes to take a little dieback without causing a lot of trouble. Next spring, don't cut them back too hard, just down to about 18 inches. Then cut out any canes that are very thin as they take away some of the nutrients for the thicker ones and you want the thicker ones as they will be the more vigorous and make better flowers. Then cut those thick canes back to 18 inches.