This is how I made the chocolate rose leaves that were on my Mum’s Birthday Party Cupcakes.

Take your leaves, and place them on a tray lined with baking paper.
Make sure you have washed them thoroughly before hand.

Melt your chocolate, depending how many leaves you need, will depend on the amount of chocolate, but you won’t need very much. 5 rows (about 20-25 grams) gave me enough leaves, with spares, for 36 cupcakes. There was plenty of chocolate left over.
Mix a dash of vegetable oil into the chocolate to make it thinner and easier to paint on.

Then using a food only paintbrush, paint the chocolate onto the leaves, and place them back onto the baking tray.
Put in the freezer until they are set.

Once they are set, gently peel the leaf away from the chocolate. It is easier to do a few at a time, because they start to melt quickly when you are handling them. If this happens, just place them back in the freezer.
I found that using the back side of the leaf that had the raised bits gave a better mold then the front side.

Quick and easy!