01 - Preheat the oven to 425°F. Line a large baking sheet with parchment paper.
02 - In a large mixing bowl, combine the olive oil, minced garlic, chopped rosemary, thyme, kosher salt, black pepper, lemon zest, and lemon juice. Add the chicken breasts and toss thoroughly to coat. Allow to marinate for at least 10 minutes at room temperature.
03 - Arrange the trimmed broccolini on one side of the prepared baking sheet. Drizzle with olive oil, then season with kosher salt, black pepper, and crushed red pepper flakes if using. Toss to coat evenly.
04 - Place the marinated chicken breasts on the opposite side of the baking sheet, spacing them evenly to allow proper air circulation.
05 - Roast in the preheated oven for 20 to 25 minutes, until the chicken reaches an internal temperature of 165°F and the broccolini is crisp-tender with lightly charred edges.
06 - Remove the baking sheet from the oven. Transfer the chicken to a cutting board and let rest for 5 minutes before slicing to retain juices.
07 - Slice the chicken breasts and serve alongside the roasted broccolini. Garnish with fresh lemon wedges for squeezing over the top.