The shed at a range of +4 to -10 C should work if you wait until they are semi-dormant. They would need water about once a month. When the temperature starts averaging +5 in the shed, they will start into growth, which is not good. I would flick off the growth buds and haul them out for a good chilling occasionally until it is safe to live outside.

Since they are good big plants, they should be OK in the garden as well, although exposed canes will be injured at, maybe, -15 C. Don't mound over the canes until they are dormant and serious cold impends. In USDA zone 5b, you don't need to plant the graft 4-6" deep. If the top is covered 3" plus some mulch, that should be enough.

Sorry if I was part of the confusing posts on wintering, SCG. There are different strategies for wintering roses already in the ground from those already in pots, and since I don't do pots I've let folks like Michael provide those responses. It's a little late in zone 5 to try planting even a well established potted rose in the ground (unless it has a 0% chance of surviving in a pot at your house like it would at mine - smile). It's possible to plant potted roses more or less any time, but you want your rose to save its strength for going dormant now, not burning energy to grow new roots in the ground.

The shed sounds like a good option for you, and you'll want to leave the rose out in the cold till it's mostly dormant - consistently -15C - and keep the pot from totally drying out for the winter. You don't want it any warmer than that, since you want the rose to stay cold. Another option is to find an unused section of your yard and winter protect it in the pot above ground using the principles in the other post circulating. Basically, you can set up something around the rose pot to hold some natural insulating material (straw, dry leaves, pine needles) and mound it well up and over the whole pot and several inches up the cane. You need more than usual insulation around the pot itself, since it's more prone to getting cold roots and drying out than a pot in the ground. I've done this with tender annuals at times and just set the pots in my vegetable garden then dumped all my yard leaves around and over the pots for the winter. In the spring, I can unearth the pots and even the annual herbs or whatever are still alive most of the time.

Bottom line is that there isn't only one method that will work, it depends on having a system that you can keep track of over the winter and keep the rose pot insulated from the cold extremes. Any rose in a pot will need one gardening zone more of protection than one in the ground, since the earth adds some protection on its own.

Cynthia

Michael, thanks for the tips. Seems that the more I research some things the more confused I become.

Cynthia, your post was absolutely not confusing but completely the opposite. I just think I researched things a bit too much and found so many varying practices that I lost confidence in what I was going to do. I appreciate the additional advice.

I would rather them in the ground as I am known for neglecting things but think I am going to stick with my original plan. That is building a small enclosure in an insulated (unheated) room in my shop and thermostatically control it to not get colder than -15C. Fortunately I am a tradesman and contractor so have everything but the thermostat. If anyone would like directions or a pictorial please let me know.

Again I appreciate all the advice. The folks here are the best.

SCG

Varying practices just tell us that there are multiple ways to succeed. If you prefer to plant them out, that will probably work. But if you decide to use the box, you should set the thermostat higher--I would say -10.