Preheat oven to 400°F and line a large sheet pan with parchment paper.
Chop the sweet potato into 1/2-inch cubes and slice the chicken breast into bite-sized pieces.
Cut the broccoli into small florets and the red bell pepper and red onion into 1-inch chunks.
In a large bowl, whisk together the extra virgin olive oil, fresh lemon juice, lemon zest, dried oregano, garlic powder, sea salt, and black pepper.
Add the chicken and all prepared vegetables to the bowl, tossing until everything is evenly coated in the marinade.
Spread the mixture in a single layer on the prepared sheet pan, ensuring nothing is overcrowded to allow for even browning.
Roast for 20-25 minutes, or until the chicken is cooked through and the sweet potatoes are fork-tender.
Serve immediately while hot, optionally garnished with an extra squeeze of lemon.