Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Peel the sweet potato and cut it into 1/2-inch cubes. Chop the broccoli into bite-sized florets and slice the bell pepper into strips.
Place the sweet potato cubes on the baking sheet, drizzle with half of the olive oil, and sprinkle with a pinch of salt and pepper. Toss to coat and roast for 15 minutes.
While the potatoes roast, pat the cod fillets dry with a paper towel. In a small bowl, whisk together the remaining olive oil, lemon juice, garlic powder, oregano, salt, and pepper.
Remove the baking sheet from the oven. Move the potatoes to one side and add the broccoli and bell peppers. Place the cod fillets on the sheet.
Brush the lemon-herb mixture over the cod and drizzle any remaining over the broccoli and peppers.
Return the pan to the oven and bake for another 12-15 minutes, or until the cod is opaque and flakes easily with a fork and the vegetables are tender.
Serve immediately, ensuring a balanced plate of protein and colorful roasted vegetables.