Prepare the brown rice according to package instructions.
While rice is cooking, preheat the oven to 375 degrees F.
Spread the red onion and red bell pepper over a baking sheet. Drizzle with 2 tablespoons of olive oil and sprinkle with sea salt. Use your hands to toss everything together to ensure the veggies are coated with oil. Bake for 25 to 30 minutes, turning once halfway through.
As the bell pepper and onion are baking, repeat the process with the yellow squash and zucchini by spreading them on a separate baking sheet, drizzling with the remaining 2 tablespoons of olive oil and sprinkling with salt. Place on a separate rack in the oven and bake for 15 to 20 minutes (or until veggies have reached desired doneness), turning once halfway through.
While the vegetables are roasting, prepare the avocado-basil crema. Add all of the ingredients to a small blender and blend until completely smooth. Add a small amount of water or more yogurt if needed for blending. Taste for flavor and add more lime juice and/or sea salt to taste.
Divide the brown rice among 3 to 4 bowls, followed by the roasted vegetables and garbanzo beans. Top with avocado crema and serve.
