Preheat your oven to 400°F (200°C) and heat an outdoor grill or indoor grill pan to medium-high heat.
Peel and cube the sweet potato into 1/2-inch pieces, then toss them on a baking sheet with half of the olive oil, sea salt, and black pepper.
Roast the sweet potatoes for 15 minutes. While they roast, chop the broccoli into florets and slice the red bell pepper into strips.
Remove the baking sheet from the oven, add the broccoli and bell peppers, and toss with the remaining olive oil and a pinch of salt.
Season the chicken breast evenly with garlic powder, dried oregano, and the remaining salt and pepper.
Place the chicken on the grill and cook for 6-7 minutes per side, or until the internal temperature reaches 165°F.
Return the vegetable tray to the oven and roast for another 10-12 minutes until the sweet potatoes are golden and the veggies are tender.
Remove everything from heat, drizzle the fresh lemon juice over the chicken and vegetables, and serve immediately.