I sprayed my roses with fungicide for rust in March and about 10 days later all the new growth looked as if it had been burned. It is over two months later and I still have no new growth or buds. Originally I thought this might be frost but neither of my neighbors' roses were affected. Besides roses in my zone (9a) don't mind our occasional 32-degree nights. Now I'm wondering if I could have inadvertently used a double dose of fungicide.
Too Much Fungicide
It sounds like either the fungicide was mixed too heavily or perhaps the fungicide was old and some chemical interactions took place. Water the rosebushes well. The following night water each of them again with a large watering can that has root stimulator and a product called Super Thrive in the same water. Wait three or four days and water again with the root stimulator and Super Thrive mix. It sounds like the rosebushes were also sent into a state of shock, the mixture I recommend will help bring them out of the shock and stress. I also recommend giving each of the large rosebushes 1/2 cup Epsom Salts scratched lightly into the soils at their bases, water it in with the mixed water I mentioned previously. This same process works well to get roses to break dormancy when they are slow doing so, gives them a bit of a "kick start" so to speak. I would not use the fungicide you have again as there could be something wrong with it. Check out an Earth Friendly fungicide called Green Cure, it is available on-line. I have not ever had any problems with it burning foliage and it works well in my Colorado rose beds.