Supposedly they are hardy to zone 5, which would be safe for Aurora, Colorado, at least during most winters. A little winter protection might be wise if you're worried, especially if they are grafted and not own-root roses. But they are probably safe for the average Aurora winter. There are plenty of reports of them surviving zone 4 winters in places like Wisconsin and Minnesota.

ok, thanks polygonum. I'll try that.

We have two chain hardware store-type knock out roses that had a very hard winter this year (as did all of our roses and everything else in our garden). We pruned a lot of dead branches, fertilized, fought off an aphid infestation, and now both knock-outs are bigger than last year, with lots of nice blooms.

thanks for the info, GLiz! My brother's not much of a gardener, but at least I'll know what to expect when I visit his garden.