Preheat the oven to 400F. Place the pepper, onion, and corn in a large mixing bowl. Add the oil and toss well. Transfer the mixture to a lined baking sheet and sprinkle generously with salt and pepper. roast for about 25 minutes, or until the vegetables are tender and some of the corn is gently browning. Remove the vegetables from the oven.
Place the hash browns on 1 or two baking sheets. Transfer them to the oven and bake for 5-6 minutes, or until crispy. Remove the hash browns from the oven and allow them to cool slightly.
Meanwhile, toss the roasted vegetables with the lime juice, black beans, and cilantro. Taste the mixture and add an extra drizzle of oil and salt and pepper to taste. Set the mixture aside.
To assemble the bowls, pile your greens into 4 serving bowls. Top each with 3 hash browns, a generous scoop of the roasted vegetable black bean mixture, and half a sliced avocado. Drizzle with cashew queso and sprinkle with cilantro, if desired. Serve.
The black bean vegetable mixture can be prepared up to 2 full days ahead of time and stored in an airtight container in the fridge.