Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
Peel the sweet potato and cut it into 1/2-inch cubes.
In a small bowl, toss the sweet potato cubes with half of the olive oil, the dried oregano, and a pinch of sea salt.
Spread the sweet potatoes on the baking sheet and roast for 20-25 minutes until they are tender and slightly browned.
While the potatoes roast, season the chicken breast with salt and black pepper.
Heat a grill pan or outdoor grill over medium-high heat and lightly coat with the remaining olive oil.
Grill the chicken for 6-7 minutes per side, or until the internal temperature reaches 165°F (74°C).
While the chicken rests, place the broccoli florets in a steamer basket over boiling water and steam for 4-5 minutes until bright green and tender-crisp.
Plate the grilled chicken alongside the roasted sweet potatoes and steamed broccoli.
Drizzle the fresh lemon juice over the chicken and broccoli before serving.