Blight or infestation on rosemary.
It's hard to tell, but spider mites could be the problem. Rosemary usually doesn't have many problems, but I do see webbing. Try this - blast the plant with a strong stream from the hose. Don't fertilize. You could use some horticulture-oil/soap spray (following all label directions) along with the treatment. If spider mites are the problem, this will help. You can go ahead and cut-out what's dead. It may take until next spring for the plant to fully recover.
Hope this helps!