Preheat your oven to 425°F.
In a small bowl, whisk together lemon juice, minced garlic, chopped fresh herbs, salt, and pepper.
Place the chicken breast in a shallow dish and pour half of the lemon herb mixture over it, letting it marinate for at least 15 minutes.
Cut the sweet potato into cubes and toss with olive oil, salt, and pepper.
Spread the sweet potato cubes and broccoli florets on a baking sheet, drizzle with a bit more olive oil if desired, and season lightly with salt and pepper.
Roast the vegetables in the preheated oven for 20-25 minutes, stirring halfway through for even cooking.
While the vegetables roast, cook the marinated chicken breast in a lightly oiled skillet over medium heat for about 6-7 minutes per side or until fully cooked and golden.
Once cooked, let the chicken rest for a couple of minutes, then slice it.
Plate the sliced chicken alongside the roasted broccoli and sweet potato, and drizzle any remaining lemon herb dressing over the top before serving.