Great question! I have my theory, but I'll wait to see what other's think.

Aren't the nematodes actually inside the roots, thus the root-knots? But I understand roses on Huey are usually good for a few years in warm, sandy soil.

Roses on Dr. Huey may do okay for a year or two, but the damage begins as soon as the nematodes kick in. The best comparison I can make is that it's very much like the slow decline that one sees in roses with RRD.

I don't know, but what have you got to lose? It's my understanding nematodes "swim" through our sandy soil. If you pot them up in good potting mix with added manure, it at least would make it an inhospitable environment for them. All of my own-root antiques are planted in my own concoction of potting mix, kitty litter and horse manure. My first antiques were planted in 2001 and are still going strong. I didn't return any of the native sand to the planting hole.

I'll pot them up and hope for the best. I may leave a few in the ground. Gentle Hermione and Geoff Hamilton seem to be growing ok. But Boscobal, Molineux and Princess Alexandra Of Kent are struggling pretty badly so I'll pot those up for sure. I'm on the fence about Belle Story.

If you dig the rose up and the roots do not have knots on them, then you should be ok. If you have knots on them you may need to cut them off. Once you go to put them in a new pot you will need to make sure that it has plenty of organic material in it. Nematodes hate the organic stuff. They prefer sand..... So when you originally planted the roses if you had put in lotss of good organics you may not have nematodes. Make sure when you have them in the pots that the pot does not touch the ground. It needs to be raised because the nematodes can travel from the ground to the pot which will defeat your purpose.

On another note, I just posted that I am having a couple of my roses decline because I have this mat that is growing and choking out the roses. I really don't know what it is and haven't gotten any answers as of yet. Someone wanted me to post a picture, but I do not have a way to do that. I haven't seen anything like it before. It looks almost like roots but they are very very dense and not actually attached to any plant. I know that this mat thing was not there when I planted the rose there last fall. This mat thing is very aggressive. I think I am going to have to remove the bush in order to dig the mat out.
Good Luck on your roses.