The caterpillar insect is the larvae of moths or butterflies. So if you grow plants that attracts butterflies you will have their caterpillar insects eating the foilage and buds of your roses.
Caterpillar garden pests sometimes feed on the leaves and buds of rose bushes, which can be very annoying to gardeners.
They leave behind round or irregular holes on the foilage and buds of roses and may chew off entire leaves or buds.
I know from experience how annoying this can be, having had to deal with the beautiful monarch butterfly's caterpillars in my own garden.
Caterpillars can be spotted on rose plants more often at night. So if you see holes on the leaves of your roses and half eaten rose buds, take a flashlight and go out after dark and pick them off and dump them in a jar of salt water. That's what I do.
I have had most of the rose buds on some rose bushes chewed up by some very hungry caterpillar insects.
I personally don't like using insecticides and chemical sprays, that's why I have "nightly flashlight trips" in my garden. But I understand some gardeners have serious caterpillar infestations and want to spray.
TO TREAT: Spray infested plants with Caterpillar Insecticides , one that specifies caterpillars, such as this one.
I also recommend using a systemic rose care product such as the one I like the best, Bayer All in One Rose and Flower Care.