I lean towards the larger/deeper once they're past the first year - the roots need some space to expand. THe smaller ones should be okay for the first year with a band.

Okay, used a conversion tool online.

1 cu ft = 7.4 gal
3 cu ft = 22.4 gal

22.4 gall seems a bit excessive, unless I'm way off. It is large. Maybe I need to find something in between? Would a 15 gal work for a long term potting?

Bands do better potted up gradually but once they're a couple of years old bigger will be better. Since those big ones are on sale you might want to grab them now and save them for when your roses mature. In the mean time I would just get some inexpensive nursery type pots to grow them up in.