Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper for easy cleanup.
Trim the ends of the Brussels sprouts and halve them, slice the carrots into thin rounds, and dice the red bell pepper into one-inch pieces.
Place the vegetables on the prepared baking sheet and toss with 0.5 tablespoons of olive oil, 0.25 teaspoons of sea salt, and 0.25 teaspoons of garlic powder.
Spread the vegetables in a single layer and roast for 20-25 minutes, tossing halfway through, until they are tender and the edges are slightly charred.
While the vegetables are roasting, season the chicken breast on both sides with the remaining sea salt, black pepper, garlic powder, and dried oregano.
Heat the remaining 0.5 tablespoons of olive oil in a cast-iron or stainless steel skillet over medium-high heat until shimmering.
Carefully place the chicken in the hot skillet and sear for 5-7 minutes per side, or until the exterior is golden brown and the internal temperature reaches 165°F.
Remove the chicken from the skillet and let it rest on a cutting board for 5 minutes to allow the juices to redistribute.
Slice the chicken into strips and serve alongside the roasted vegetables, finishing the entire plate with a fresh drizzle of lemon juice.