My first comment does not seem to have been posted, so I'll write it again.
These last few years I've been having problems with die-back on several of my new implants (that is, roses I planted out last fall,which is the proper time here in Italy). They look fine until the end of July, and then suddenly this thing that some people call the "creeping black finger of death" shows up. A black blotch appears at the base of a main cane (the laterals don't show this) , and when I cut it off, it is obvious that the cane is basically dead, since it's completely brown inside. This year this began early, in July, and Pacific Dream was one that got it-it's now reduced to only one cane. I assume this is canker,and I'm guessing that it may be caused by temperature swings-extreme heat for a month or so, followed by the arrival of a cold front that is strong enough to reach the Italian peninsula. The fact is that we had a horrendous month of June, and then it suddenly turned "normal" (well, what used to be "normal" 25 years ago). I myself seem to get sick when this happens , a sort of virusy-type sindrome. Maybe this makes roses get sick too? What is your climate like? Is this the kind of die-back you are experiencing?