Adding pesticides to your spray solution indiscriminately will kill beneficial insects and increase your chance for a spider mite infestation. If you spot a bug problem, spray the problem area with the appropriate chemical. Check your garden for aphids as soon as new growth emerges. Aphids appear as soon as the weather warms and they feed on new growth. Blast the critters off with a strong spray of water or mist the tops of plants with insecticide to keep foliage clean.
Roses love to be fed regularly.
Roses need lots of food for foliage and bloom. High rainfall and frequent waterings tend to leach fertilizer out of our sandy coastal soil. Many rosarians feed their roses every other week. Add organics and work them into the soil. Pre-mixed organics are available in garden centers and specialized vendors.