Preheat your oven to 400°F and line a large baking sheet with parchment paper.
Dice the sweet potato into half-inch cubes and slice the red bell pepper into strips.
Toss the sweet potatoes, broccoli, and bell pepper on the baking sheet with 0.5 tbsp of olive oil, 0.25 tsp of salt, and the dried oregano.
Roast the vegetables for 20-25 minutes, tossing halfway through, until the sweet potatoes are tender and the edges are slightly caramelized.
While the vegetables roast, season the chicken breast evenly with garlic powder and the remaining salt and pepper.
Heat the remaining 0.5 tbsp of olive oil in a large 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 and the internal temperature reaches 165°F.
Remove the chicken from the pan and let it rest for 5 minutes before slicing.
Plate the roasted vegetables alongside the chicken and finish with a fresh squeeze of lemon juice over the entire dish.