Black spot that bad would not have appeared overnight. I would blame the alcohol and perhaps the peroxide. The problem with many home remedies is that they can be toxic to different plants and in different concentrations. I also like to warn about using vinegar to kill weeds. The vinegar is left in the soil to disturb all the living little soil microbes and this is detrimental to the health of the living soil. If you want to go natural then use a strong jet of water to destroy aphid and spider mites and keep roses clear of other tall plants to increase air flow and discourage fungal infections like black spot. I do think the foliage may fall off your rose plants but don't worry you will get a second chance as the rose will sprout fresh new growth soon. Keep growing, Marianne Binetti