If it has been real hot where you are at, it is normal for the rosebushes to drop lots of leaves. It is an effort by them to get more air flowing through the rosebushes to help keep them cooler. If it has been real wet where you are, it could be too much water and the water is choking the oxygen out of the soils around the rosebushes. Once things dry up a bit they should improve in such a case. Here are a couple links to a couple articles I wrote on this subject. Please check them out and hopefully they will help you as well:
Answered on August 23, 2012
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