I doubt the aphids killed your roses.

But whatever the case, aphids are easy to limit. A harsh water spray blasts them off. Or direct hits of insecticidal soap kills them. And repeat every several days.

I sprayed my roses with fungicide, followed up with insecticide, and must have gotten a combo of this on my skin. The black spot is gone, the aphids are gone, and I have blisters all over my wrist where I got it on me. So please, wear gloves! I learned my lesson (Ow)