Heat oven to 400°. In a medium saucepan, heat 2 teaspoons coconut oil over medium heat. When oil has melted, add onion and stir to coat. Reduce heat to medium-low, and cook onion 8–10 minutes, until fragrant and translucent.
While onion is cooking, place coriander in a small pan and toast over medium heat, 5–8 minutes, until fragrant and slightly browned; frequently shake pan to toast evenly. Remove from heat; transfer to a spice grinder or mortar and pestle, and grind.
Add ginger, garlic, lemongrass, ½ teaspoon salt and half of ground coriander to onion mixture; stir to combine. Cook 2–3 minutes, until fragrant.
Add 1 cup coconut milk and rice; stir and cover to cook over low heat 35–45 minutes, until liquid is absorbed and rice is creamy. Remove lemongrass.
While rice is cooking, combine cauliflower and chickpeas on parchment-lined baking sheet. Drizzle with 2 teaspoons coconut oil, add remaining coriander and ½ teaspoon salt, and stir to coat. Roast in oven 35–45 minutes, or until browning; stir halfway through.
Remove cauliflower and chickpeas from oven, and place in large sauté pan with ¼ cup coconut milk. Cook over medium-low heat 3–5 minutes, until combined. Stir in cilantro and salt, to taste.
To serve, scoop rice on plates with a ½-cup measuring cup, and serve cauliflower mixture alongside. Garnish with cilantro and chile peppers.