Here is a picture showing the "Christmas Tree" pattern of magnesium deficiency. It is interveinal chlorosis with some green remaining between the yellow and the vein itself.

Dr. Malcolm Manners says boron can cause the same symptom if the soil is acid, so a pH check is called for.

Here is a link that might be useful: UF image

It is almost surely a nutritional deficiency, probably magnesium if it is on the older rather than new leaves. Magnesium can be supplied by Epsom Salts, 2 TB per plant. However the deficiency can be caused partly by high soil pH or an excess of some other nutrient such as potassium. You might want to get a soil test.

michaelg,

thanks for the quick reply....how do I get my soil tested? I will purchase the Epson salt this weekend and will treat the roses right away. Will this deficiency totally kill the rose eventually if left untreated?

In most states, inexpensive soil tests are available through the extension service. Look in the phone book, under the county, for "cooperative extension" or "agricultural extension." If you get a test, you can bring the results here.

I doubt it would kill the plants, but affected leaves will not function much, and the symptoms will gradually spread up the cane.

BTW the boron symptom is caused by an excess, not a deficiency, and according to Dr. Manners when pH is below 5.5.