Dab the chicken breasts with a paper towel to dry. Remove any fat and chop the chicken into 1/2-inch pieces. Place in a medium bowl.
In a small bowl, combine the parsley, oregano, garlic powder, onion powder, paprika, seasoned salt, and pepper. If desired, mix in the red pepper flakes for a bit of heat. Stir everything together until well combined.
Add half of the seasoning mix to the bowl with the chicken along with 2 tablespoons of olive oil and the zest and juice of 1 lemon. With your fingers, toss everything together until the chicken is nicely coated. Cover and place in the fridge for about 30 minutes while you prepare the vegetables.
Preheat your oven to 425°F. Line a very large sheet pan with parchment paper for easy clean-up later on. This not only helps with the clean-up but also ensures the vegetables roast evenly.
Halve the baby carrots lengthwise and cut the baby red potatoes in half or quarters if they’re large. Coarsely chop the onion into sizeable pieces, about 2-3 sections for each half.
Spread the carrots, red potatoes, and onion evenly on the prepared sheet pan. Drizzle with another 2 tablespoons of olive oil and sprinkle the remaining seasoning mix over the top. Toss everything together with your hands until well coated.
Place the sheet pan in the preheated oven and roast for 20 minutes. The vegetables should start to become tender during this time.
Meanwhile, chop the broccoli into bite-sized pieces. Once the 20 minutes are up, carefully remove the pan from the oven. Toss the vegetables to ensure even cooking and create space on one side of the pan for the broccoli.
Add the chopped broccoli and minced garlic to the other half of the sheet pan. Toss them with the last tablespoon of olive oil and the last teaspoon of seasoning mix. Make sure everything is well coated.
Now it’s time to incorporate the chicken. Remove it from the fridge and drain off any liquid. Add the chicken to the sheet pan, ensuring it’s spread out and not piled on top of itself.
Return the pan to the oven and roast for another 15 to 20 minutes. You’ll know it’s done when the chicken registers 165°F and the vegetables are at your desired tenderness. For an extra touch, switch the oven to a high broil for the last 1 to 2 minutes—watch closely to avoid burning!
Once out of the oven, top the dish with freshly grated Parmesan cheese. Serve immediately or store for meal prep by dividing into containers with cooked quinoa or rice.
