Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper for easy cleanup.
Prepare the chicken by cutting it into 1-inch cubes; halve the Brussels sprouts, slice the carrot into rounds, and chop the bell pepper into bite-sized pieces.
In a small bowl, whisk together the extra virgin olive oil, fresh lemon juice, dried oregano, garlic powder, sea salt, and black pepper to create the marinade.
Place the chicken and all vegetables into a large mixing bowl, pour the lemon-herb marinade over them, and toss thoroughly until every piece is evenly coated.
Spread the mixture in a single layer across the prepared baking sheet, ensuring there is enough space between pieces to allow for proper roasting.
Roast in the center of the oven for 20 to 25 minutes, tossing the ingredients halfway through, until the chicken is cooked through and the vegetables are tender and slightly caramelized.