My experience is that some varieties actually do not do well on their own roots, that many modern roses, on their own roots are not as hardy. For example, I will deep plant a bush, with the union 4" below the soil level. Buried branches sprout roots that are killed off overwinter. I would suggest you try
planting your bush very deep, such as with the bud 4-6" below the level of the soil. You will in effect be invoking a propagation method called "stooling", but since you will just state that you are deep planting, and not stooling, then no one can accuse you of wrongdoing. Although we all know you are propagating, in your heart you know that you just want a hardier plant, so you may proceed. The buried branches will root. If these roots are vigorous and hardy, they will take over from the rootstock, and you will be able to separate a rooted plant in a year's time. Observe how well it grows on its own, compared to the original bush. Since you are conducting research, this is alright. Once you have tried the bush for several years, then you must kill the original bush. Make sure that you have written out the experiment in a little book, with the future date shown when the original bush is to be killed, and write down your observations, so no one can challenge that this is a research project, and NOT a propagation project. Make sure that the time line for the experiment is long, that way the patent may have run out by the time all of your years of experimentation are done, and you won't even have to sacrifice the original bush. Sativa.

On the issue of grafted plants, you might want to try a different rootstock. There are vendors who sell grafts on R. multiflora rootstock. None of my roses of R. multiflora have ever suckered, but then only three of the 100+ roses I have grown on Dr. Huey have ever suckered.

I just wanted to let you all know that I found out this Betty Boop does grow well on its own roots! YAY!