First off, aphids are insects, not a disease. second Volick is a dormant spray, I wouldn't use it on new growth. Aphids are easy to control with just a blast of water. No spraying needed. You may have to cut back the damaged area and let it regrow again. I don't think you caused any serious damage. What kind of temps are you having now?
Another thing, did you read the labels? That is the first thing you should always do!

The Volk label does recommend 5 tbs/gallon for the growing season. Nothing on the Ortho label mentions chlorothalonil plus oil but the link below for a different chlorothalonil product does (under the heading, Tank Mixing), "Do not tank mix chlorothalonil with oil or with any adjuvants which contain oil as their principal ingredient".

Your roses do seem to have spray burn, but a lot of those spots on the leaves look like spot anthracnose.

Here is a link that might be useful: Chlorothalonil label

Ah, the usual spring problem rears its ugly head yet again - Aphids. The cheapest, most environmentally friendly way to get rid of them is not to spray them at all. Email me directly and I will supply the answer just as I do every spring.