Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper to prevent sticking.
Scrub the sweet potato and carrots; dice the sweet potato into 1-inch cubes and slice the carrots into 1/2-inch thick rounds.
Mince the garlic cloves finely to ensure the flavor distributes evenly across the dish.
Slice the chicken breast into 1-inch thick strips or bite-sized pieces to ensure they cook at the same rate as the vegetables.
In a large mixing bowl, combine the chicken, sweet potato cubes, and carrot rounds.
Drizzle with avocado oil and add the minced garlic, dried rosemary, dried thyme, sea salt, and black pepper.
Use your hands or a large spoon to toss the ingredients until every piece is thoroughly coated in the oil and herbs.
Spread the mixture onto the prepared baking sheet in a single layer, making sure the pieces aren't too crowded so they roast rather than steam.
Roast in the center of the oven for 25 to 30 minutes, tossing halfway through, until the chicken reaches an internal temperature of 165°F and the vegetables are tender.
Remove from the oven and drizzle with fresh lemon juice to brighten the flavors before serving.