It looks as if there are a few things going on here. It is hard to see clearly but there is possibly rust on the leaves (the yellow spots). You could confirm this by turning the leaf over and if you see dusty orange spots, it’s most likely rust. Rust is a fungal disease. Here is a link that might be helpful: http://www.ipm.ucdavis.edu/PMG/GARDEN/PLANTS/DISEASES/rusts.html
The lower petals that are dark in color suggest either extreme heat or not enough water. You would be the one who would know that.
We are also wondering if you pruned your roses back in the winter as is customary. If not, you could have alot of old wood and foliage that are carrying diseases and/or pests over from last year. A proper pruning in the winter give roses a chance to rest and revive themselves for spring. If you choose to do this next year, be sure to properly dispose of all plant parts so as to not spread the diseases and pests that might be present.
Here is another link that you might find helpful:
http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7465.html
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