Thank you for your question, Dan.  There are several reasons that rose stems develop swelling, described in this Extension article:  https://apps.extension.umn.edu/garden/diagnose/plant/annualperennial/roses/stemsdying.html

I am afraid that, without more information, and perhaps a closer examination of the tissue, the photos aren't enough.  I suggest that you take these samples to the Clackamas County Extension office, where Master Gardeners can help.  https://extension.oregonstate.edu/clackamas

Good luck!