Since your question has been unanswered for a day--I have no experience, but at least two people have posted about this in the past. The roses on Fort. did fine in clay soil. Growers farther north reported decreased winter hardiness.

One thing you should be aware of: the very high graft and long shank below it are mechanically weak. You need to drive a couple of pieces of rebar next to the crown and tie them firmly to the bases of canes. Otherwise a large plant can break at the graft.

I am not an experienced grower, but I talked to a man at our local rose society. He grows many roses of different types and has a lovely garden. He swears by fortuniana stock. Our soil is hard clay and rock, so I think it probably does well in clay.
Thanks for the rebar idea, michael.
Rooty

If OP is on the west side of Houston and gardens (or tries to) in the heavy dark gray clay around Rte 6, Fortuniana (and most other roses) have problems growing in it, unammended. Gypsum and composted rice hulls gave me a rose garden in that horrible stuff.

Fortuniana can grow very well in pots. Large pots are the key and in the heat of Houston you won't have to worry that much about winter freezes. The most magnificent modern roses I've seen on fortuiana were in pots in these locations: east of Tampa, near New Orleans, and in coastal Carolina.
All were in potting soil and were well watered with fairly high care. The productivity of modern HTs on fortuniana would make many of us cry with envy.
The late Johnny Becnel grew many of his HTs on Fort. in raised beds that left much less room for the roots than would be expected from the size of the above ground bushes. He was a true plantsman and knew to keep the roses well watered and fertilized out on the delta near the mouth of the Mississippi.

Thanks for all your responses! I contacted the Antique Rose Emporium and they told me that fortuniana needed excellent drainage. They said I could grow it in a very large pot (like the size of half-barrel), but after a few years it would probably get root bound and I might have to take it out and do a root pruning possibly. They said it would be better to either a) plant it in the ground and get a rotor tiller and mix in a bunch of compost into the clay or b) a raised bed. I don't have a rotor tiller, and I didn't feel like digging in compost (lazy) and the area I planted it had other things planted there in the past, with some good soil mixed in from years ago. So, I built a raised bed on top of this area, to make sure that the drainage was good. I used good potting soil, soil conditioner, manure, compost and topped with mulch. I noticed the rose already had wooden stakes around the base of the graft tied to the rose (to prevent the rose from breaking at the graft). Do you think this will suffice, or should I replace the wooden stakes with rebar? Thanks!!!!!

I used rebar on mine and found it to be unnecessary. The roses grow very fast with fortuniana and tend to have very strong bases. Now if you have a rose in an exposed area with little around it that would be another matter, I suppose.

Thanks for the info!!!!