By putting a stone on a long stem that is touching the ground. Put the stone a ways in from the growing tip. Within two months, there will be roots coming from at least one leaf node in contact with the ground.
(This also worked for its offspring Out of Yesteryear which is two or three generations removed.)

Did you try to root it in the plastic bag? For me it gave much higher success rate with other cuttings, since the outside method somehow did not work that well for me here. You basically put some moist sand in the plastic bag (I put it in a pot to make sure that it does not tilt, etc), stick cutting into it and keep it tied for a month or so (can add water, but make sure it is warm, not cold tap one). You need to keep it warm, but not frying in a sun.

But bracteata thrives in hot dry conditions. It's not a rose for gentle growing conditions.
If I were given cuttings, I might try an almost dry alkalin sand.

Not all roses like the same conditions. Compare the difference in rooting for chinas and teas based on times of the year.

Ann and elemire, thanks for the responses. Okay, I need to experiment, keeping in mind however that I don't have a rose to get cuttings from: these came by mail from a gardening forum acquaintance on the island of Elba. I do regularly fail with roses that other gardeners root with ease, Noisettes being the great example. Possibly summer rooting would work with these (or dormant cuttings in winter for other varieties). I've never done summer cuttings because it's so dang dry then, sunny and windy; and rooting under plastic bags has never worked for me either. Also most summers I've been away for several weeks. Perhaps next year I may be in a position to take cuttings in May and June, having finally a place out of the sun and wind that might work for a summer nursery.
I tried the layering trick with 'Koenigin von Daenemark' which I could never get to root, because I had a grafted plant that I wanted to spread out and take over a section of terrace. The last time I checked it, it looked as though the layering might have worked. Since then I went to Florida for a month and a half and that garden has turned into a jungle of weeds, still remaining to be dealt with.
Melissa

Melissa,
Sometimes weeds are good because they keep the humidity up but not too much.
For your noisettes, I've found that I get better roots (and very fast) if I take a cane that's pencil sized either in spring or fall. I have lost canes to spring canker and have salvaged them by cutting the cut off thing into multiple cuttings (well above the canker). The best and fastest takes were from the pencil sized pieces and they also made massive roots rather fast (sort of logical, they had more stored material from the larger stems to work with.)

I also sort of believe that the rose shouldn't know that you want it to tip root. That way it happens faster.

Peg a growing tip into the soil (layering), as Ann suggested. Pretty much the only way to root R. bracteata. Cuttings rarely work. :-(

hmmm, yep, i have rooted Mermaid (pretty much the only HB i have come across) as though it was a blackberry (tip-layering) but of course, you need a live rose to do this. Mermaid can be a bit tricky as a semi-ripe or hardwood but even so, still had more success than with the evil pimpinellifolias!

Ann,
I don't regard weeds as the worst thing that can happen to a garden, but I'd rather have the mulching effect from my garden subshrubs and herbaceous perennials along with some of the more attractive native annuals. We have an awful lot of bindweed and Bermuda grass. I'll keep in mind what you say about Noisette cuttings.
Paul, thanks for the tip. It's good to see you, by the way.
Melissa

'Mermaid's not in the same class of difficulty as R. bracteata: I've managed to root it a couple of times. Don't know about the Pimpinellifolias.