Preheat your oven to 400°F (200°C) and line a large rimmed sheet pan with parchment paper for easy cleanup.
Peel the sweet potato and dice it into 1/2-inch cubes; chop the red bell pepper into bite-sized pieces and break the broccoli into small florets.
Cut the chicken breast into 1-inch chunks to ensure they cook at the same rate as the vegetables.
In a large mixing bowl, whisk together the extra virgin olive oil, fresh lemon juice, dried oregano, garlic powder, sea salt, and black pepper.
Add the chicken chunks, sweet potato cubes, broccoli, and bell pepper to the bowl, tossing thoroughly until every piece is well-coated with the herb marinade.
Spread the mixture in a single, even layer across the prepared sheet pan, making sure not to overcrowd the ingredients so they roast rather than steam.
Roast in the center of the oven for 20 to 25 minutes, or until the chicken is cooked through and the sweet potatoes are tender and slightly caramelized on the edges.