To ground the rose leaves: place them in a spice grinder together with 1 Tablespoon of the rest of the blend and grind - this way, it will grind easier.
Place all the ingredients in a sealed jar/container and shake well.
Keep in fridge or freezer.
You can buy a ready-made Ras-El-Hanut mixture (a reliable brand), check the ingredients, and add missing spices such as mace, cardamom, ginger, and rose petals.