In a large pot, bring rice to a boil with 6 cups of water. Once boiling, reduce heat to low, and simmer for about 60-65 minutes, stirring occasionally, until the rice is very soft and has started to fall apart.
In a small bowl, use a mortar and pestle, crush the saffron with 1/2 tsp sugar, then pour 2 tbsp of hot water over it. Stir until dissolved.
Stir the saffron water, ⅓ cup sugar, and rose water into the rice. Cook for an additional 5 minutes, stirring constantly. Remove from heat and let cool for 30 minutes.
Divide the pudding evenly among individual bowls.
In a food processor, blend the steamed sweetpotatoes with honey and cardamom. Top each bowl with 2 tbsp of the blended sweetpotato, using a knife to swirl it into the pudding.
Garnish with slivered almonds, dried rose buds, cinnamon, and cardamom, if desired. Enjoy warm or place in the fridge to cool. The pudding will harden as it cools.