Bring sugar, 1⁄2 tsp. saffron, and 1⁄2 cup water to a boil in 2-qt. pan over high heat. Add 1⁄2 cup orange peel; cook until tender, 8–10 minutes. Let cool, and stir in rose water; set aside.
Make the rice: Rinse rice in a strainer under water until water runs clear. Place rice in a 6-qt. pan. Add salt and 4 cups water, and cover; soak for 2 hours. Place pan over high heat; boil. Cook until rice begins to rise to the surface, about 12 minutes; drain. Return pan to medium-high heat; add remaining saffron, milk, and oil. Return rice to pan, forming it into a mound; using handle of a wooden spoon, poke 5 holes in the mound (to let steam escape); cover, and cook for 15 minutes.
Pour butter and 1 cup boiling water over rice; cover. Reduce heat to medium-low; cook until a golden crust forms on bottom, 30–35 minutes. Transfer rice to a platter, separating the grains as you go; break up crust from bottom of pot, and stir into rice. Garnish rice with candied and remaining raw orange peel, carrots, almonds, and pistachios.