Elena - on another rose forum there are posts from rose growers in your zone and even further north. It does sound like a struggle to find roses that will reliably survive the cold. One source that I've bought from is Palatine nursery located just over the Niagara Falls border in Canada. Their roses are grafted on multiflora stock and and seem to do well in colder climates, and in my northern California garden as well! I just received an order last month and the bare roots are doing extremely well.