The question is, did it die because of the stems turning black, or did the stems turn black because it died of a root infection that cut circulation off to the stems? You can see by the wrinkled texture of the still-green portion of the canes that no circulation is getting up to the canes from the roots. They are shriveled. Look at the roots, are they rotted, soft, gooey? Did the soil smell sour and foetid when you pulled the rose out of the ground? Is the area constantly soggy? Those conditions would point to rot. Is it possible a large pet dog urinated several times on the rose and gave it such a blast of ammonia that the rose was poisoned? Did it accidentally get too much fertilizer? That would point to death by chemical damage. A bacterial infection would be another possible culprit--are there other problem plants in your yard?

its fall ... the leaves will fall off.. along with whatever is attacking the leaves... nothing to do there ... but clean them up afterwards ... EVERYTHING looks like this in fall ... these would be great plants for you to learn about pruning ... there is some historically bad pruning ... maybe for the fence install ... the further one.. you could probably cut to about 3 inches.. and with no insult to the root mass it will be 4 feet tall again by next summer ... and then in the next few years ... having either succeeded or failed.. then you can get rid of them ... or not ... they are what we call.. a short lived tree ... in tree years.. that mean about 20 years max.. if you are lucky.. and the garden gods favor it ... getting rid of it.. is not that big a deal ... see you in the shrub or tree forum.. if you are interested in gardening.. and learning to prune... ken ps: the link shows.. what well pruned specimens should look like ... in a variety of forms .... Here is a link that might be useful: link

It looks like there may be some sort of root damage or root infection. However, I'm still learning myself and interested to hear what others with more experience say and/or would do to save it...

I was going to say look for sawfly larvae on your damaged plants, but they don't bother canes. Any chance deer are coming through and stripping your roses? If so, I'd spray them with a repellent (I've had great success with Liquid Fence Deer & Rabbit Repellent) and see if the damage stops.