I had almost forgotten about this old method, which I once tried. It was a miserable failure.
As I recall, you were supposed to plunge the cutting into a potato and plant the potato in the ground. It might have worked if I hadn't planted the potatoes, I suppose, and had just used the potato as a temporary growing medium, but I ended up with lots of big potato plants growing in the middle of my rose beds. No trace remained of the roses that had been planted in them.
What are the instructions for the method you'll be trying, Flowerpetal?