Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper. In a mixing bowl, toss the diced sweet potatoes with olive oil, chili powder, cumin, smoked paprika, garlic powder, salt, and pepper until evenly coated. Spread them out in a single layer and roast for 25–30 minutes, flipping halfway through, until they are tender inside and slightly crispy on the edges.
While the sweet potatoes roast, cook your brown rice or quinoa according to package instructions if not already prepared. Warm the black beans in a saucepan over low heat, seasoning lightly with salt and a pinch of cumin if desired. Chop the tomatoes, slice the avocado, dice the red onion, and prepare any additional toppings so everything is ready for assembly.
Start by adding a generous scoop of rice or quinoa to the bottom of each bowl. Top with roasted sweet potatoes, black beans, corn, cherry tomatoes, red onion, and avocado slices. Sprinkle shredded cheese over the warm ingredients so it slightly melts, then add a dollop of Greek yogurt or sour cream, fresh cilantro, and a squeeze of lime juice before serving.