Preheat the oven to 425 F.
In a small bowl, combine the chilli powder, onion powder, garlic powder, paprika, cumin and oregano.
Add the cauliflower, corn, and chopped red pepper to a baking sheet lined with foil. I like to keep them separate just in case some vegetables cook more quickly than others. Drizzle with olive oil and sprinkle evenly with the spice mixture. Toss with your hands to coat evenly.
Transfer the pan to the oven to roast for 20-25 minutes until vegetables are browned and tender.
While the vegetables are roasting, process the dressing ingredients in a blender, food processor or with an immersion blender. Alternatively, you can finely chop the garlic and cilantro and whisk with the remaining ingredients.
To assemble, divide the brown rice between 4 bowls and top with the roasted vegetables and beans. Sprinkle with cheese and cilantro if desired, and drizzle with the dressing.