Preheat your grill to medium-high heat and your oven to 400°F for roasting the sweet potato.
Slice the sweet potato into 1/2-inch rounds or cubes, toss with half the olive oil, salt, and pepper, then spread on a baking sheet.
Roast the sweet potatoes in the preheated oven for about 20-25 minutes until tender and lightly browned.
While the sweet potatoes are roasting, prepare the chicken by patting it dry.
In a bowl, mix the juice of the half lemon, the remaining olive oil, mixed herbs, salt, and pepper.
Marinate the chicken breast in the lemon herb mixture for at least 10-15 minutes.
Place the chicken on the preheated grill and cook for about 6-7 minutes per side, or until the internal temperature reaches 165°F.
Steam the broccoli in a steamer or microwave until bright green and tender, about 4-5 minutes.
Arrange the grilled chicken, roasted sweet potatoes, and steamed broccoli on a plate and serve immediately.