Hi Caitlin,

This is a gray blister beetle. And yes, their damage can be extensive. I don't believe rose is a host? 

Your best management is to have a bucket of soapy water and knock the beetles into it. Their populations are high, but short-lived. Wear gloves, as the beetles can cause serious irrigation. Following collection, wash your gloves and hands/clothes.

There are insecticides that can be used, but because these are on flowering plants, you risk harming beneficial pollinators.

Here's more information: https://webdoc.agsci.colostate.edu/bspm/arthropodsofcolorado/Clematisblisterbeetle.pdf

Thank you .