Hi Cecily,

This looks like peony leaf blotch. The most effective ways to prevent this is to make sure the plant isn’t crowded, aiding air circulation, and good fall cleanup. Fallen leaves should be removed every fall and the plant should be cut to the ground before winter.

You should prune the affected stems off at the ground. Here’s more information:

https://bygl.osu.edu/node/1182

Your rose should be fine.

Hope this helps!

You’re welcome.