I don't think roses on Fortuniana can go dormant. I've growns (and continue to grow) both R. x fortuniana and four or five roses on fortuniana.
From it's parent R. laevigata, fortuniana gets genes that make it grow through winter and to set bloom very early in spring. Remember that where it comes from, winter is not what we know as winter...it's just shorter daylight.
Fortuniana roots keep pushing nutrients and wanting to grow into the above ground parts, whether they are fortuniana or something else put on by grafting or budding.

Jimmy Moser out in warm, warm Memphis years ago wrote about overwintering his roses on fort...in plywood boxes that fit over his roses.

That said, you need to grow a rose on fort in conditions where it never slows down. It's both eyeopening and a bit depressing because never will you and I get growth like that, short of moving way far south with the flying cockroaches and fire ants and buckmoth caterpillers and chilli thrips and need to air conditions six to eight months of the year. WIth two decades in Houston and NOLA, I say that without wistfullness.

As usual, thanks very much Ann. I'm trying to think of ways to finagle it, such as making sure they come outside on days with light and warmth as soon as possible, and then head back in until I'm certain that frost is gone for the season. Maybe use the grow light I've got. But I'm certain I'll have to special order the pots they grow in, and then make sure to use a dolly when moving them. That's a whole other side to this story.

I really envy the kind of production the growers who use fortuniana can achieve. Maybe I'll try just one (famous last words). What's a twenty-five dollar investment, plus S&P, anyhow?

If its in a greenhouse, I would not worry about it, as you will protect it from the winter. Size may be a problem, but you can always trim.

Now, now, I haven't seen a roach in ages. And today I was fertilizing and composting rose beds with the sun on me and the temp in the 70's. It's called balmy weather. If the Victorians could grow Teas and big Noisettes "under glass", I'm sure you can grow roses on Fortuniana in your greenhouse. Will it be heated?

You do have shorter days up there than we do in "fire-ant heaven", but Ann will have to say if that will make much difference. Personally, I'd order some teas and Noisettes myself. Go for it! How cool to have a greenhouse, august!

Sherry

Gee Ann, after reading your comments, I'm almost scared to live here on the Gulf Coast (lol). At least I haven't seen any of those dreaded Chili Thrips (shudder). The rest of it, yes, I have to deal with those. I'm just glad to never have to battle Japanese Beetles!
As for a "need" to go dormant, if your greenhouse conditions are warm enough, great. I have had only a few roses on fortuniana; never thought much about dormancy. But my own-root roses often don't go dormant because the winter can be mild enough that it doesn't trigger them to go dormant. When that happens, you still need to do some kind of pruning in late winter to prepare them for a robust new season. I prune mine moderately, snap off all the old leaves (leaves are only meant to live 4-6 months anyway), leave any new basal growth or brand new leaves that sprout on the parts of the bush I haven't pruned, and I leave it at that. Getting rid of the old leaves sends a signal to the plant to get ready for spring flush.

Just strip 'em and prune 'em.