well in your zone your in ground roses freeze as dep as the roots go.. so having them freeze in a container is no diffrent.. the problem for me is in the early spring the containers will heat up lots faster then the ground and the on and off freezing and heating with the sun of the late winter days.. gets them pumping up water to the plant and then another freeze.. I mulch with what's available to keep the sun off the roses and the container.. best in the shade in the winter.. Gordon

Dig a trench for your containers. Lay the containers in the trench and cover with a mulch of pine shats or leaves or something similar. All the better if you can do this up against the house or in a semi-protected area. That'll take care of the freeze-thaw problem and is similar to the way many people winterize their in-ground roses in colder zones. Also, be sure to check the hardiness of any rose you purchase. There are many that won't survive a northern winter.