Heat olive oil in a large skillet over medium heat.
Sauté diced onion and bell pepper until softened, about 5 minutes.
Add minced garlic, cumin, and chili powder; cook for another minute.
Stir in the cubed sweet potatoes, black beans, rice, and vegetable broth.
Bring mixture to a boil, then reduce heat to low and cover.
Simmer until sweet potatoes and rice are cooked through, approximately 20 minutes.
Season with salt and pepper to taste, and fluff with a fork.
Garnish with fresh cilantro if desired, and serve warm.