I'm not 100% sure but it could be thrips. I have so many rose blooms that are brown and nasty from those rotten bugs. I'm also seeing yellow dead buds on other roses. Are all your buds dying before they open or just a few? You probably don't want to hear this but my Purple Pavement is having an excellent year..

First, it's probably not thrips. It could be partially because of the aphids, and the weather certainly isn't helping, but I have to say that your spraying might be making the situation much worse than it would otherwise be. Rugosas should never be sprayed, except to use a jet of water to remove the bulk of the aphids, because they tend to be sensitive to many chemicals. If your plant isn't getting a great deal of sun, that might also exacerbate the problem.

Fortunately, aphids tend to be more of a seasonal nuisance and your plant should recover to bloom normally later in the season. Aphids are especially fond of rugosas, as you've noticed. Just be sure to avoid sprays other than water unless you've thoroughly tested them on small sections of the plant to see if they are safe to use. From my experience with insecticidal soap, it can harm sensitive plants and I would personally avoid it.

Stefan