I was given a piece of a thornless running rose bush and told to just stick it in water and it will root. Is that true?
Your best shot is to buy growth hormone, wet the shoot that will be the root
place it in soil that is for growing seeds, cover with a plastic (spray water lightly first) and out it in your kitchen window.
I have rooted many plants just by sticking it in a huge pot I have next to my front door, it gets sun buts is sheltered. Also I have rooted tomato clippings
begonia, onions lettuce, spinach, LOL just by putting the root in a bit of water.
After they develop root I set it in a small pot
By the way where did you get a thornless rose, I have lymphadema and cannot have rose.