Although I have no experience with this root stock, I assume that if you plant it deep and get through a couple of winters, the rose will have developed its own roots.

Of course this theory depends on the assumption that it will actually rain in Tennessee in the future...

But you don't want the roses to go own root, because Fortuniana is a rootstock that makes for more blooms than almost every rose could make on its own.
Many serious exhibitors near Nashville and Memphis grow some of their bankers on Fort. Those roses got the same damage as everyone else's this past Easter freeze.
But the problem with roses growing on fort (personal experience) is that there is no such thing as winter dormancy. The roses keep putting out new growth through winter (the same as the rootstock does when grown as a rose bush) and that new growth gets killed. There is also no tendency for established canes to harden off, and that makes for additional cane loss over winter.
Adding mulch to the plant may just cause cankers to the canes if we have a wet winter, mulch won't slow down the plant's intention to keep growing through winter.

Just thinking out loud here, but if they don't exhibit winter dormancy, do they exhibit drought dormancy? It's something I would like to try with HTs here, however I would have to find a way to turn off the tropical storms first.

Just based on my plants of R.x fortuniana and R. laevigata (half parent of fortuniana), both are still growing through this horrific dry summer.(Neither gets irrigation or spray of any kind.) Maybe not as fast as the winter growth, but both still have fresh leaves and no cane abandonment as a result of the rose choosing to abandon certain canes.

Ann, thank you for your very informative response. No wonder my Julia Child has been such a continuous bloomer! I thought she was just a great performer but I guess having it on Fort rootstock increased her success during our miserably hot, dry summer. I hope I can keep her over the winter. Maybe as an experiment I can purchase one this spring that would grow well in a large pot that could then be overwintered in my garage.

Rosalita,
I have one rose, Susan Louise, that's a close descendent of R. gigantea. I love this rose. Winters, even our mild ones, want to kill SL's canes.
Now we cover SL with a huge plastic trash can or large paper box in the colder weeks in winter and uncover it those weeks that temps are above freezing. I'm trying to get some established woody growth (which is often more freeze tolerant).
This fall, when it cools off, take a look at the new growth on Julia Child and see if it could be covered when temps are forecast to be below 22F.
Cane retention is important.

Thank you for this tip! Julia Child is in my back yard so the neighbors won't be bothered with seeing a trash can or cardboard box over her. I am definitely going to try that and will let you know how she fares this Spring.