Adjust an oven rack to the middle position and heat the oven to 425°F. Toss the cauliflower, oil, cardamom, cumin, salt, and pepper together in a bowl until the florets are evenly coated.

Spread the cauliflower onto a rimmed baking sheet and roast until tender and the edges are starting to brown, about 15 to 20 minutes.

Heat the remaining oil in a large saucepan over medium-high heat until it shimmers. Add the onion and cook, stirring frequently, until they are soft and dark brown around the edges, 10 to 12 minutes.

Stir in the garlic, jalapeño, cinnamon, ginger, cardamom, and cumin and cook until fragrant. Add the rice and stir until the grains are well coated with oil and slightly toasted, about 1 minute.

Pour in the water and salt and bring to a simmer. Reduce the heat to low, cover tightly, and cook until all the liquid is absorbed, 16 to 18 minutes.

Remove the pot from the heat and sprinkle the currants and saffron over the rice without stirring. Place a clean, folded dish towel over the pot, then secure the lid on top; let it sit off the heat for 10 minutes to finish steaming — the towel absorbs moisture so the grains stay separate.

Gently fold in the cilantro, mint, and roasted cauliflower with a fork to fluff the rice. Season with salt and pepper to taste and serve warm with the yogurt sauce.