Place rose petals and caster sugar in a food processor or blender. Process until you get a pink rose sugar, and the rose petals are mixed well with the sugar.
Spread out the rose sugar on a dish/platter, and let it dry at room temperature between 2-4 days. Mix it a few times a day.
If you want finer sugar, you can put the rose sugar in the food processor or blender one more time after it has dried.