Prepare the couscous by placing it in a bowl and covering it with 500ml boiling water. Let it stand for 10 minutes until the water is absorbed, then fluff up with a fork. Soak the raisins in lukewarm water for 15 minutes until softened, then drain. Toast the almonds and pine nuts by placing them in a dry frying pan over a medium heat and stirring for 2 to 3 minutes, until golden brown. Roughly chop the pistachios and add to the couscous. Add the raisins, almonds, pine nuts, cinnamon, sugar and rosewater (if using) and gently toss together. Serve warm or at room temperature with a few gratings of orange zest (if using) to garnish. Warm and serve the milk on the side for pouring over.