In more severe climates, you may need to use a rose
collar and/or protect the canes however even these
solutions do not completely cover the entire plant
with mulch.

I don't have to worry about this anymore, but am I
mistaken in thinking that the white coverings that
some people place over their roses (are those the
collars you're talking about??) are more to keep
it from being smashed/broken by the weight of the
snow than to keep it 'warm'? Even when living in
Minnesota, I never covered my roses and they did
pretty well. Didn't lose any of the 3 large and 6 or
seven miniatures that I had over the course of 3
winters.

Tracey