If possible, use a half a wine barrel. Hops roots like some room to breathe, the bigger the better. I have heard of people doing well with them in wine barrels. I think HomeDepot and lowes will sell them for like 20-30 bucks. And they will still smell like wine. haha.
The hops may not get as tall or be as full, but they should be good. Don't expect much the first year. My hops had mixed results, even in the ground. This year (year 2), they are all up and starting to climb.
You will need to have something they will climb that is at lead 10 foot tall. it is possible to get them to run along fences or tie a rope up to the roof and let them go.