Preheat oven 425 degrees. Cut the cauliflower into bite-sized florets. Arrange in a single layer on a large baking sheet.
In a small bowl, combine the turmeric, coriander, garam masala, curry powder and 1/2 tsp. of salt. Sprinkle evenly over the cauliflower. Drizzle with 2 Tbsp. of olive oil. Then, toss the cauliflower so that it is coated in the oil and spice blend. Roast for 25-30 minutes.
Heat the remaining 2 Tbsp. of olive oil in a heavy nonstick skillet over medium heat. Saute the onions, garlic, ginger, serrano peppers and 1 tsp. of salt until tender, about 5 minutes. Lower the heat, stir in the coconut milk and simmer over a low flame until smooth. Stir in the cauliflower and gently toss to coat.
Make the coconut rice: Bring coconut milk, broth, sugar and salt to a boil in a saucepan. Stir in the rice. Lower the heat and simmer, covered, 15-20 minutes, until liquid is absorbed, stirring occasionally. Fluff with a fork.