Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Mince the garlic cloves and whisk them in a small bowl with 0.5 tablespoon of olive oil, dried oregano, dried thyme, sea salt, and black pepper.
Pat the chicken breast dry and rub half of the prepared herb-oil mixture evenly over all sides.
Place the broccoli florets and trimmed asparagus spears on the baking sheet, then toss them with the remaining herb-oil mixture until well-coated.
Nestle the chicken breast onto the baking sheet among the vegetables.
Roast for 18 to 22 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are tender and slightly charred.
While the chicken rests for a few minutes, warm the pre-cooked brown rice in a small pot or microwave.
Whisk the remaining 0.25 tablespoon of olive oil with the lemon juice to create a light finishing sauce.
Slice the chicken into strips and serve over the warm brown rice alongside the roasted vegetables, drizzling the lemon-herb sauce over the entire plate.