Hmmm...I'm kind of lost here. My nice expensive clay and ceramic containers cracked and broke after freezing one winter, so I've been converting to plastic containers since then. I found some foam types that look like concrete. A few of the nice ceramic ones just had cracks, so I put a plant in a basic black plastic pot, then set that down inside the pretty container.
Are you thinking the plastic pots won't make it through the winter? Or that they don't provide enough insulation?
For the heavy concrete pots I use for annuals, I cover them in the winter so they don't freeze, expand and crack. On most I just use a big plastic saucer and set a brick on that. In the pots that have roses, if there's space in between the black plastic pot and the good pot, it does fine all winter. Just as Neal said, if a rose is rated to zone 5, it does ok in a pot in the winter. Drifts in particular grow well potted. I love how they "drift" over the edge.
Right now, Lowes has some huge colorful (jelly bean colors) plastic pots for $10. REally huge, big enough to grow a tree for years. They also had some plastic whiskey barrel looking ones. They have knock outs for drain holes. I'm using one to grow a small lotus, and another with the holes knocked out to grow a few new roses.
