Hi Sabrina!
I have never heard about propagating roses from leaf cuttings. To the best of my knowledge, it is not possible - one requires part of the stem with a leaf-bud. I usually leave about three leaf-buds on my cuttings but I have read about people striking cuttings with only one bud and even halving the stem length-wise but have never tried it.
Not professing to be an expert only experienced
