Tip: Make sure you buy a flower nail at a craft store. It will make this whole process a breeze. Start at the center making a Hershey kiss out of frosting. Using a rose petal tip (I used Wilton # 104) make small 'rainbow shapes' around the base. Continue to add layers the same way until you have the desired size rose you want.
Here is a video from one of the cake decorating websites. Check it out...