That may depend upon where you're located. I've successfully wintered over "new roses" (Zone 7), that is, those in pots as you've described, by digging a hole large enough to hold both pot and rose in their eventual planting spot . Leave approximately one third of the rose canes sticking out of the soil, packing the remainder of the hole with dry leaves and/or unfinished compost well above the cane junction near the base of the plant. Heap up leaves around the plant as possible and cover on particularly cold nights or days with a 5 gallon WHITE bucket (transmits some light). Note that the bucket is there primarily to keep your insulating layer of leaves in place and should be removed if temps start to rise above 35-40 degrees F.
At planting time, situate the plant at the proper soil level and amend as is your usual custom.
Good luck!
Steve

I'm in zone 7a.

Unfortunately, they're already planted and have been for a week. How do you think I should proceed in that case?

Just cover with dry leaves and they'll probably make it just fine.

In zone 7a you need to water them regularly, but especially if we're expecting a hard freeze. The roots will be growing during the winter and even though the top of the plant will go dormant the roots will continue to grow. It probably would be a good idea to mulch heavily.