The temps given are not really all that high. However if the rosebushes are located where they get direct sun at the most intense times of sun heat during the day, they could be under stress. Keeping them well watered is more important than feeding them too much at such times. Watering them with water that has a product called Super Thrive in the water helps them deal with all kinds of stresses and shocks, thus I recommend it if you can get it. I get the large sized bottle of it on Ebay for a good price. The other thing you can do is to provide a lightly colored shade structure for them during the hottest time of the day. Such as white of light colored umbrellas tied to poles sunk in the ground by the rosebushes. The light coloring helps reflect the most intense rays of the sun. Dark colored ones will increase radiant heat upon the roses, which you do not want.
