I have a recollection of reading something about overwintering plants in containers saying to consider your plant as growing 2 zones colder than what you're currently in. If that holds true, then being in zone 7 with roses hardy to zone 5, they may be just fine. Regardless I think with minimal protection you'd have great chances of keeping them.
Mika, Austins are a bit pricey here too, and almost always more than the rest of a vendor's offerings from other breeders. The bare root plants from the Austin site were around $25 each (about $5-$8 more than other bare root roses from other vendors), but potted plants at garden centers are closer to $50.
