Except for Fortuniana, which as a rootstock isn't hardy north of z7, the issue is the grafted variety itself and if the graft union is protected. In winter, many problems occur due to dehydration.

On your standards overwintered indoors, how are they handled? Is the soil in the pots kept moist? Dehydration is the biggest problem. Also, just being "greenish" does not mean that the plant was still alive, it could have been on its way out when you bought it.

Diane,Thank You for your response,

Is there a way to tell is a rose has died, other than waiting for spring?

Not really.

The thing that really brought this home to me was the year I was doing some late pruning on Alexandre Girault. For some reason that I don't currently remember, the long, cut off canes were left outside all winter. They were perfectly green in the spring, and it took several weeks for them to finally turn browns.

Something that seems a remarkable difficult concept to get across is that 'freezing' at 25°F, 'freezing' at 10°F, and 'freezing' at -10°F are very, very different experiences for anything that is actually out in those temperatures. So the pots in my garage usually 'freeze' on and off during the winter. However, it's rare (I haven't seen it yet) for the garage to go below 25°F, and everything usually winters over fine.