Pickering and Hortico sell bare-root grafted plants, so they're not measurable in quarts or gallons. Grafted roses are typically grown in the field for at least two years before they're sold, so they're much bigger than most own-root roses.
I used to love Hortico and I have hundreds of Hortico roses living happily in my garden, but they started going downhill a couple of years ago, to the point that even customers of long standing have given up on that nursery.
Where did the $23 come from, by the way? Hortico is selling the rose for $14.99.
You could take a chance on ordering it from Hortico. They may have learned a lesson from so many of their customers abandoning them, but my best advice is to wait until the end of September, when Pickering updates its Website and starts taking orders for 2011, and order it from Pickering instead.