My roses are rusting! Well not really, but they are getting rust spots(orange spots) on the underside of their leaves.
So to combat the problem, all fallen leaves are raked away. Watering is kept to the base to control the spread of the rust and ample air circulation is provided by clipping any leave that is not up to par.
Organic gardeners don't like harsh chemicals so 1 tsp baking soda in 1qt water is mixed and sprayed on the bush.
Some people use sulfur powder every other week when new foliage is developing. I have not tried this so I have no idea how well it works.
Some people swear by neem oil spray. From my research it looks like there is no way to cure, only prevent.