It's not necessarily the cold but the wind and freeze thaw cycles that kill the roses. Overwintering your potted roses in a dard unheated garage or shed will protect them. Tender roses will still experience dieback and the soil ball will freeze solid but your roses should survive OK.

Did you mean tea roses or hybrid tea roses? There is an important difference. To avoid confusing us, please use the proper term so we don't have to clairify which you're talking about.

If you like floribundas, by all means use them. Choose a variety that doesn't get too big or you'll require a very large pot that'll be really heavy to move into the garage.
Smaller shrub roses, polyanthas, minifloras, and miniatures all make good potted plants.

Water is important as many overwintered potted roses are lost to drying out. A shovel full of snow occasionally will suffice. Just don't let the soil dry out completely.
I use potting soil. I like Miracle Grow or WalMart's Expert Gardener brand. The Expert Gardener has a lot of large pieces of organic material and small wood chips in it while the Miracle Grow potting soil is lighter with lots of peat moss. Both contain a slow release fertilizer so additional fertilizers are not required although I will, on occasion, mix aged horse manure with them. I add nothing for drainage as the bottom pot holes allow plenty of drainage. I water until it drains from the holes, then I know the soil is saturated. Don't use bagged garden soil as it's too heavy and will compact.
I don't cut mine back until spring although really tall bushes will be shortened a little to make them easier to handle. I do all my pruning in the spring.

Where you are, the problem isn't going to be keeping them warm enough, but keeping them cold enough. Ideally, they should be kept around freezing. So in your climate, they will spend extended periods of time warmer than that.

The usual recommendation for around there is to keep them outside, against the south wall of the house. However, to have plans for bringing them in the garage for relatively brief cold snaps.

Thanks for all the advice. I think I could put the pot on the south facing wall overwinter. Do you mean cold snaps in late winter and spring? (like we had this year?) I can't see myself dragging it into the garage for a cold snap so maybe just covering it if there is one would work.

You'll have to do something to keep it warm when the temperatures get into single digits. Covering them simply keeps some heat in. It doesn't create any heat.

Plants cooled off during the evening in winter face added stress in an eastern location during early spring when the warm sun rises in the morning and strikes the plant causing their night chilled cells to heat up too rapidly and burst or be damaged enough to allow canker to set in. It happens here to my eastern potted roses, and I even lost a Crabapple tree to this type of freeze damage. If possible move your pot to a south or west location where it can gradually warm up and and cool down.......As for rocks in the pots, new finding show that they are at best not necessary for drainage, and at worst can actually impede drainage. I no longer use them.

I just use Miracle grow potting mix and there moisure control potting mix which I really, really like so far.
I was using a potting soil, but, the brand I was using was to heavy, so, after reading a thread on container soils, (to use potting MIX) I switched.