Answer: Usually, defoliation is a sign of stress. It can be caused by over or under watering or by insects or disease. In roses, perhaps the most common reason would be a fungal infection such as black spot. Whatever the cause, this needs to be addressed because without leaves the plant will eventually die. Without knowing the symptoms other than "no leaves" it is a bit difficult to make a guess or give suggestions. However, you might want to look through the Q&A information on black spot and other rose problems and see if you think that is it. Alternatively, you might take a look at a book or two about roses and see if you can troubleshoot from there. One book I particularly like because it is very straightforward and has lots of good explanatory diagrams and illustrations is "Roses for Dummies" by Lance Walheim, Dummy Press, ISBN 0-7645-5031-4.
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