In a medium-size saucepan, bring orange juice to a boil. Add carrots, garlic, rosemary and orange peel. Simmer, partially covered, until carrots are softened and juice has reduced by almost half, about 15 minutes. Then add water and salt. Cover and bring to a boil. Turn off heat but leave pan on burner. Stir in couscous, cover and let stand until liquid is absorbed, about 5 minutes. Fluff with a fork. Sprinkle with pine nuts and onions, if using, then stir in.