Preheat your oven to 400°F and line a large baking sheet with parchment paper for easy cleanup.
Peel and dice the sweet potato into 1/2-inch cubes, then toss them on the baking sheet with half of the olive oil, a pinch of sea salt, and black pepper.
Roast the sweet potatoes for 15 minutes.
Add the broccoli florets to the baking sheet, drizzle with the remaining olive oil, and roast for an additional 10-12 minutes until the vegetables are tender and slightly browned.
While the vegetables roast, season the chicken breast evenly on both sides with the dried rosemary, garlic powder, and the remaining sea salt and black pepper.
Heat a non-stick skillet over medium-high heat and sear the chicken for 5-7 minutes per side until the internal temperature reaches 165°F.
Remove the skillet from the heat and drizzle the fresh lemon juice over the chicken to deglaze the pan and add brightness.
Plate the chicken alongside the roasted sweet potatoes and broccoli, drizzling any remaining pan juices over the top.