All the roses I have ever grown have all been growing on their own roots. I haven't dug up very many roses, but the ones I have dug up have been fairly shallow rooted. With one notable exception ... the old tea rose 'Adam'. Adam is a fantastic rose, and I loved it, but had to remove it because it became too large for my smallish garden. It had high quality, sturdy, deeply growing roots. They were what you'd hope for in a plant. I felt sick after digging it up. With roots like that, it could have lived for decades. What a loss to the garden, I miss it to this day.

Randy

Tausendschoen (meemaw's smoke house rose) had lived next to a smoke house in total shade for so long that the family remembered it as a yellow rose. It had shallow, massive woody roots but the center looked like Paul Bunyon's broom handle and went down over four feet. It could not be pulled out.
R. multiflora platyphylla (the almost century old one that came with the farm) had a woody root core, but depended on near surface roots that went out over twenty feet.(all of which sprouted RRD..so we know the depth that we had to pull them from)
Souv. de St. Anne's also managed some shallow very woody roots that reached out six feet in three years. (We shouldn't have moved it.)

Perhaps the strangest roots were on Hero from Pickering. When planted the multiflora looked like all the other multiflora they graft onto. When we moved it at two years the roots came up easily , were about eight inches deep and looked for all the world like a giant upside down afro. When we moved it yet again the roots were back to looking woody like other roses. The interim stage ...darned if I know why...one possibility is that the soil was so much better in the upper eight inches that the plant adapted and made gazillions of small roots.

About Hero-- when we plant a grafted rose deeper than it grew in the field, the first thing it seems to want to do is put out feeder roots from the shank, graft, or canes. Most roses seem to be very dependent on shallow feeder roots regardless of soil. I recall one of those afros, also on a plant that had been in for a couple of seasons, and one that I had planted deeper than usual.

Late last night, I remembered something from yesterday afternoon. A duh moment if ever there was one.
In our sandier soil at the bottom of the hill, I found it extremely easy to weed around some of the more recently planted fenceline roses...the reasons were that moles and voles had worked the soil under the grass roots really well and the grass roots were very short and easy to pull out.
So...a localized cultural feature would be the response of a rose to putting down deeper roots because shallow roots would be a buffet.
The mole/vole problem could also curtail a rose's natural tendency to sucker.

I have an old Aloha in a bad spot, only about a foot of soil raised up over bedrock, plus it is the moles' favorite area. The rose wilted a few times when it was younger, but doesn't seem to mind them now. I would love to see an x-ray of the root structure in relation to the mole voids. In this case, there's no escape downward. There is a bank behind, though. When I turn the hose on this area full bore, the water just disappears except for what runs out underneath the timbers.

What is the natural structure of gallica roots?

I had to pull out a young Buff Beauty, and it had roots 5' long, broomstick thick, going everywhere. My eyes just about fell out of my face. I've always wondered if it would make a good rootstock.

Ann once said a gallica is not an it. It is a them. The suckers run out just barely under the surface and are real easy to dig up while weeding. There is this horizontal stick with a rose stick rising up and what looks like barely any roots. So you stuff the thing back under the soil and it usually makes it. I've had no luck transplanting them. Usually forget about it long enough to forget to water a day and it goes to rose heaven. Got a theory that you might do better with seed.

I'd forgotten that, Deb. Back when I first met a mature gallica, the roots were so different from what I thought they'd be.
What Hoovb says about what would be a good rootstock makes great sense. And maybe some of us (looking in a mirror) need to put things into perspective... a rose that grows well, here, and will take a graft (cleft probably) well...
Would make better roses here, for those roses for whom own-rootness isn't a good thing. (SdlM).

The lists of rootstocks out there that have been used is huge. Did the world of US rose producers go Huey because it makes a small root at year two?

Below I've linked to the Heritage Rose Foundation website where you'll find a copy of Dr. Griffith Buck's article on rose rootstocks.

Here is a link that might be useful: Dr. Buck's article

Buck doesn't comment much about root structure, except that Ragged Robin has extra fibrous roots.

Multiflora has fleshy roots that diverge into finer fleshy roots and so on. It doesn't seem particularly deep in my garden, but then I have shallow soil. I never planted multiflora-based roses until five or six years ago. Most of the ones I have dug were plants that were not doing well and didn't have good root development. One that I dug because I didn't like it had grown huge roots in a short time.

There is also the Royal Horticultural Society's Botanical Study of Rootstocks from the 1930's.
A huge amount of data as part of a student's MSc.
I was able to get a copy from the original at our ag library.
http://worldcat.org
is the search engine I use to find the copy of books and papers closest to my zip code.

Here is a link that might be useful: A discussion about the Study of Rootstocks