Preheat your oven to 400°F and line a large baking sheet with parchment paper.
Trim and halve the Brussels sprouts, peel and slice the carrots into rounds, and roughly chop the red onion.
In a large bowl, toss the vegetables with 0.5 tbsp of olive oil, half of the sea salt, and half of the black pepper.
Spread the vegetables in a single layer on the prepared baking sheet and roast for 20-25 minutes until tender and slightly charred.
While the vegetables roast, season the chicken breast evenly on both sides with the remaining sea salt, black pepper, garlic powder, and dried oregano.
Heat the remaining 0.5 tbsp of olive oil in a heavy-bottomed skillet over medium-high heat.
Place the chicken in the skillet and sear for 6-7 minutes per side, or until the exterior is golden brown and the internal temperature reaches 165°F.
Remove the chicken from the heat and let it rest for 3 minutes before slicing.
Serve the sliced chicken alongside the roasted vegetables for a clean and balanced meal.