Preheat the oven to 425 degrees. Toss the sweet potato cubes with 2 tablespoons olive oil, cumin, chili powder, salt, and black pepper on a baking sheet.
Spread the sweet potatoes in a single layer and roast for 25 minutes, stirring once halfway through, until the edges turn golden and the centers soften.
Let the roasted sweet potatoes cool for 10 minutes on the baking sheet.
In a large bowl, combine the cooled sweet potatoes, black beans, red bell pepper, red onion, and cilantro.
Drizzle the remaining 1 tablespoon olive oil and the lime juice over the mixture. Stir gently until everything is evenly coated.