I know I'm still looking for the best rootstock. I believe that generally, the roses that grow well on their own roots do better in my garden than roses that do not. But that may simply be because such roses are generally more vigorous.
Where I live in the mountains of Arizona the soil has a high pH and multiflora rootstock - which starts out quite vigorous - will often fade away after a year or two. My experiments adding powdered sulfur have not changed this materially, Not yet. I also have pocket gophers that nibble on rootstock. I've been told that gophers prefer Dr. Huey. So I'm not sure its a good choice. I've lost to gophers own root roses, roses on multiflora rootstock, and roses on Dr. Huey rootstock. I think the total is around six or eight with roughly equal numbers on each stock. So maybe Dr Huey is not worse than other rootstocks in this location. If one does the statistics, I think one will find it to be at least as good as multiflora.
Dr Huey is blamed, too, for spreading PNRV. People who grow roses in places that every summer get above 110F claim that the virus is not a problem. Viruses tend to break down at such temperatures and if I remember correctly holding roses at such temperatures has been used to rid some roses of PNRV. But studies in other locations suggest material lack of vigor can be an effect of the virus. The PNRV issue was a big thing in the 1980s and 1990s, but the advent of so many good own-root nurseries has meant that much less attention has been focussed on it recently. And certain nurseries have worked very hard to eliminate the problem from their stock.
I've been told that it's too cold in the winter here for Manetti or Fortuniana rootstock. But I have also been led to believe that in slightly warmer climates fortuniana is the best. At least when HT roses are concerned. I've come close to doing the experiment for myself.
So far, I have yet to find a rootstock that is suitable for my kind of high pH soil, frosts, and heavy feeding by gophers. My garden houses something upwards of 200 rose plants, and I spend quite a lot of time obsessing over how to manage gophers, drought, high pH, and other soil fertility problems.
My own opinion is that the first question in selecting rootstock is whether a rose cultivar is available and will do very well in a location on its own roots. If the answer is "yes" and the plant does not sucker, then it seems to me that - at least provisionally - the answer is to start with a plant on its own roots. Usually, one simply does not know; and if one does the experiment, too often one will find the answer is "no." I have a six year old Sheila's Perfume on its own roots that has not yet reached eight inches high. It is precisely the size it was when I took it out of its pot in 2012. It is my understanding that - especially with hybrid tea roses bred in the twentieth century - the primary reason to buy a rose on budded rootstock is to make it possible for the thing to actually grow. And that is the reason I buy HT roses on Dr. Huey rootstock. I also buy David Austin roses on Dr Huey rootstock because most cultivars are a little hard to come by on their own roots. And as a practical matter, if a rose is unavailable on the rootstock of choice, then one must choose between not growing it or growing it on a less than perfect rootstock choice.
A second issue is whether rose suppliers can reliably and competently produce rose plants on the rootstock they use and deliver those roses alive to your property. Each year the answer seems a little different. Palatine almost always does a flawless job of budding onto multiflora rootstock. (But longevity proves a problem here with soil pH above 8.0) Edmunds does a very good job budding onto Dr Huey and growing the plants to a large size before selling them; but they store their roses under such poor conditions, (based on 2017 experience), that fully a third of the plants are stone cold dead on arrival. And more than half of the rest need daily attention for three months until established. Many of those that live prove to be stunted things, clearly not proving the benefit of budded rootstock. Two years ago I got some good budded roses from J&P. This year, the batting average is closer to zero for six.
Two decades ago own root roses shipped from (then) Heirloom Old Garden Roses were barely rooted cuttings, and were not viable unless they spent a full year in a pot in a nursery. Vintage Gardens own root roses were about ten times as big on arrival, but although I bought many dozens, only a handful survive; and none of the hybrid tea roses have. The own root roses I've gotten in the last two years from Rogue Valley Roses have generally done quite well in pots. A few have been planted out and continued doing well. I have had some good fortune with own root roses from Antique Rose Emporium, especially with old garden roses and with Kordes roses. The three or four roses from Chamblees have done even better.
The only HT roses I have on their own roots are Beloved, Chrysler Imperial, and Joyfulness. Joyfulness has just enough vigor to actually grow, slowly and tentatively. The other two, not so much. Some of the reason for success with roses from RVR, ARE, and Chamblees is that the cultivars they sell tend to be materially easier to grow here than HT roses, regardless of rootstock.
Last year I lost probably half the budded roses I planted despite daily attention. This year I lost most of the budded roses that did not originate at Palatine. I find that it is slightly less disspiriting to lose my roses more slowly due to a long series of local insults such as dry weather, frost, six kinds of nibbling animals, and occasional neglect than it is to lose half a large order within weeks of delivery mostly to lack of adequate care on the part of the supplier. So I've started to shift my focus to own root plants, especially in cases when the rose is not a hybrid tea rose. (Obviously not every HT rose is the same and it may be that in some cases own root HT roses will do as well as budded ones. If so, I'd be happy to know which ones,)
I think it's just incredibly silly to imagine that there is one "best" solution for every single cultivar, location, climate, soil, and so on. ARS publishes the top ten best cultivars for each of its half dozen or dozen different geographical areas. Some cultivars make several lists, but in general, each cultivar has benefits and drawbacks that make it well suited to one location and less so to another. In much the same way, I think different rootstocks may have different advantages in different places. I am, however, still waiting to discover the right one for growing HT roses in my area.
