From the product label, it is Neem Oil, which is a decent product. Caution, ANY OIL, of any type, CAN fry your foliage if the weather is too hot, too dry, plant is too dry, sun is too intense. Follow the directions precisely as far as when to spray, how much, how frequently and what weather conditions to avoid are concerned. Used properly, under the appropriate conditions, it should take care of many insect and disease issues, but believe the cautions about burning foliage. Oils of all kinds CAN burn under the right conditions. Kim

Here is a link that might be useful: Product label

Thanks for the quick response, Kim.

The directions are very general (spray weekly if treating for fungicide; biweekly if using as preventative ) and mentions nothing specific about amount for application or any time preference. Knowing that roses are a bit particular about the timing of watering, pruning, etc., I figured that there was more to this fungicide than applying it once a week but maybe that's not the case here.

Already sprayed them tonight (got antsy to spray because I let the blackspot get embarrassingly bad); so am glad that I did so and not in the AM because the weather forecast for the next week is supposed to be pretty hot (high 80's to mid 90's, full sun).

Would hate for the leaves to sizzle. Geez. That would be awful. Thanks for the forewarning then. Now am wondering if I got a little over zealous with my spraying.. Ugh. If its not one thing, it's the other :-D

You're welcome. From what I see about the label on line:

VEGETABLES, HERBS, SPICES, ROSES, HOUSEPLANTS, FLOWERS, TREES,
AND SHRUBS.
APPLICATION INSTRUCTIONS
ferti-lomeî
ROSE, FLOWER & VEGETABLE SPRAY is an effective fungicide for the prevention and control of various Fungal Diseases including Powdery Mildew, Black Spot, Downy Mildew, Anthracnose, Rust,
Leaf Spot, Botrytis, Needle Rust, Scab and Flower, Twig and Tip Blight, and Alternaria. As a preventative,
apply ferti-lomeî
ROSE, FLOWER & VEGETABLE SPRAY on a 7 to 14 day schedule until the potential
for Disease development is no longer present. To control Disease already present, apply ferti-lomeî
ROSE, FLOWER & VEGETABLE SPRAY on a 7 day schedule until Disease pressure is eliminated. Then
continue spraying on a 14 day schedule to prevent the Disease from reoccurring. To prevent Rust Leaf Spot
Diseases, Anthracnose and Scab, begin applications at the first sign of Spring budding. To prevent Powdery
Mildew, apply in mid-Summer or when Disease is first detected. Continue applications until Disease pressure no longer exists.
MIXING INSTRUCTIONS
Mix ferti-lomeî
ROSE, FLOWER & VEGETABLE SPRAY at the rate of 2 tablespoons (1 fluid ounce) per
gallon of water. Thoroughly mix solution and spray all Plant surfaces (including undersides of leaves) until
completely wet. Frequently mix solution as you spray.

Hopefully, you didn't exceed the 2 TBS per gallon. Even at that rate, if your weather is expected to be as hot as you've indicated, you might experience some burn. But, what is worse? Scorched leaves of black spotted, falling foliage? You're right, it's always something! Your higher heat is going to help prevent some of the disease spread because it can get too hot for the spores to germinate. Until it begins remaining cooler, I wouldn't spray be once every two weeks for fear of burn. Good luck! Kim

Since oil sprays are not very effective against blackspot, I would avoid spraying in the evening because the water in the spray, staying wet overnight, might cause germination to occur. (It is certain that blackspot needs long wetting to germinate, but I am just speculating about the effect of oil spray.)

In the morning, plants are cool and well hydrated, so sprays are less likely to burn. Sprays will dry quickly, which is good for a number of reasons. Be sure the soil is well moistened before applying sprays, especially oil, sulfur, chlorothalonil, or bicarbonate.