What's left of the rest of the plant? I've had ROS with suddenly dead big branches, and they keep on going. If the rest of the shrub is leafed out, it should be okay. Could you post a picture of the whole shrub, just in case?

I agree that a photo of the whole shrub would help. The green on the branch in the last photo isn't a problem - it's lichens growing on the bark surface that don't cause any harm.

where are you in z5

we had two miserable winters in z5 MI

ken

Here's a photo of the whole shrub. The branch that broke off was just as green as the ones here. I'm in Milwaukee and you're right, especially winter before last. We didn't get hammered as hard last year though. Do you think winter damage weakened it? Is hard pruning next Feb/March going to be my best course?

My FIL had some issues with his ROS this spring. Nothing like that but the top foot of the plant seemed to have perished over the winter. His is an older one like yours as well. In your case, it doesn't look like that branch was super healthy to begin with. You might prune much of the top growth next spring and see what you're left with. If your plant is in decline, try nursing some of the inevitable seedlings that start every year...come to think of it though, I'm not sure ROS comes true from seed. Perhaps a few cuttings are in order. My ROS is in it's 4th year planted in our garden. Every year it has tons of seedlings, some of which I let grow and are now decent sized sprouts. A few of those sprouts might bloom this year so I'll get to see if mine have come true from seed.