I've had a lot of trouble with clematis getting clematis wilt. But if it is that, you will know it. All the leaves rapidly wilt like this, going from healthy to dead in a few days:
If you have that, best thing to do is cut any affected stems off at ground level and dispose of them (NOT in compost pile).
If your leaves are just yellowing/ spotted, but not wilting, it is something else, maybe some other kind of fungus.
Cut off all the affected leaves and then spray everything, including the roses with a baking soda solution, tablespoon of baking soda to a gallon of water.
Let us know how it works!