Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Peel and dice the sweet potato into small 1/2-inch cubes, and chop the broccoli and red bell pepper into uniform bite-sized pieces.
Slice the chicken breast into even 1-inch strips or cubes to ensure they cook at the same rate as the vegetables.
In a large mixing bowl, whisk together the extra virgin olive oil, minced garlic, dried oregano, sea salt, and black pepper.
Add the chicken, sweet potato cubes, broccoli, and bell peppers to the bowl, tossing thoroughly until every piece is glistening with the herb oil.
Spread the mixture in a single layer on the prepared baking sheet, making sure not to overcrowd the pan so the vegetables roast rather than steam.
Roast for 20 to 25 minutes, tossing the ingredients halfway through, until the chicken is golden and the sweet potatoes are tender.
Remove from the oven and immediately drizzle with the fresh lemon juice to brighten the flavors before serving.