Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Dice the sweet potato into 1/2-inch cubes and chop the bell pepper and zucchini into bite-sized pieces.
Place the sweet potato, broccoli, bell pepper, and zucchini on the baking sheet; drizzle with half of the olive oil and season with a pinch of sea salt and black pepper.
Roast the vegetables in the oven for 20-25 minutes, tossing halfway through, until the sweet potatoes are tender and the edges are slightly caramelized.
While vegetables roast, season the chicken breast with dried oregano, minced garlic, and the remaining salt and pepper.
Heat the remaining olive oil in a cast-iron skillet over medium-high heat. Once hot, add the chicken and sear for 6-7 minutes per side until deeply charred and the internal temperature reaches 165°F.
Remove the skillet from heat and squeeze the fresh lemon juice over the chicken, allowing it to rest for 3 minutes.
Plate the charred chicken alongside the roasted vegetable medley and serve immediately.