Wash, peel, and grate the carrots. Place in a saucepan and add 2 cups water and the sugar. Bring to a boil, stirring constantly until the sugar completely dissolves. Reduce heat to low, cover, and simmer for 30 minutes.

In a large Dutch oven, heat the oil over high heat and gradually add the rice flour while stirring constantly. Cook for 5 to 8 minutes or until the mixture turns lightly golden.

Reduce heat to low. Wear oven mitts and carefully add the cooked carrot to the hot rice flour (step back to avoid getting splashed). Add saffron-rose water and cardamom and cook over low heat for another 15 to 20 minutes, stirring quickly and constantly with a long wooden spoon to make a thick, smooth halva (the consistency of peanut butter).

Place a 10-inch ring on a flat serving platter and spoon the halva into it; pack firmly with a spoon. Garnish with ground pistachios, walnuts, rose petals, and cinnamon. Allow to cool, lift up the ring, then cover and chill in the refrigerator. Serve either as a main dish with lavash bread or alone as a dessert.