Preheat your oven to 425°F (220°C).
In a small bowl, combine lemon juice, olive oil, chopped rosemary and thyme, salt, and pepper to create the marinade.
Pat the chicken breast dry and rub the marinade evenly over it.
Place the chicken breast on a lined baking sheet.
Cut the sweet potato into 1/2-inch cubes and toss with a little salt, pepper, and a drizzle of olive oil; spread on a separate baking sheet.
Trim the ends of the green beans and season lightly with salt and a few drops of olive oil; arrange them on the baking sheet with the sweet potatoes if space allows or on a separate tray.
Roast the chicken, sweet potatoes, and green beans in the oven. Roast the chicken for about 20-25 minutes until cooked through and the edges become slightly crispy; roast the vegetables for about 20 minutes, stirring halfway through for even cooking.
Check that the chicken reaches an internal temperature of 165°F (74°C).
Plate the roasted chicken with a serving of sweet potatoes and green beans, and enjoy your nutritious, flavorful meal.