01 - In a large bowl, whisk together 3 tbsp olive oil, garlic, parsley, thyme, rosemary, lemon zest, lemon juice, 1 tsp salt, and 1/2 tsp pepper until well combined.
02 - Add the chicken breasts to the marinade, turning to coat thoroughly. Cover and refrigerate for at least 15 minutes, or up to 2 hours for deeper flavor.
03 - Preheat the oven to 425°F. Line a large baking sheet with parchment paper.
04 - Toss the broccolini with 2 tbsp olive oil, 1/2 tsp salt, 1/4 tsp pepper, and chili flakes if using. Spread the broccolini on one side of the prepared baking sheet.
05 - Place the marinated chicken breasts on the opposite side of the baking sheet, spacing them evenly.
06 - Roast for 22 to 25 minutes, until the chicken reaches an internal temperature of 165°F and the broccolini is tender with crispy edges.
07 - Let the chicken rest for 5 minutes, then slice and serve alongside the roasted broccolini with lemon wedges and extra fresh herbs if desired.