I start by preheating my oven to 400°F and lining my baking sheet with parchment paper. This step matters more than people think, since a hot oven from the start is what gives you that golden roasted edge instead of a soggy, pale dinner.
In a mixing bowl, I toss the halved baby potatoes with half the olive oil, garlic powder, Italian seasoning, salt, and pepper. Potatoes take the longest to cook, so I always give them a head start on the pan before anything else goes on.
I spread the potatoes out on the sheet pan and roast them alone for about 15 minutes. This little head start is the secret to avoiding undercooked potatoes sitting next to perfectly done chicken.
While the potatoes roast, I rub the chicken breasts with the remaining olive oil, smoked paprika, salt, and pepper. I like to pat the chicken dry first with a paper towel, since removing extra moisture helps it brown instead of steam.
Once the potatoes have had their head start, I push them to one side and nestle the chicken breasts onto the pan. Everything goes back into the oven together for another 15-20 minutes.
With about 10 minutes left, I toss the green beans with a little olive oil and salt, then scatter them around the pan. Adding them late keeps them bright and slightly crisp instead of mushy.
I always check the chicken with a meat thermometer at this point, looking for an internal temperature of 165°F. If the potatoes need a few more minutes to crisp up, I just leave everything in a little longer.
Once everything is done, I pull the pan out, squeeze fresh lemon juice over the top, and sprinkle on parmesan if I'm using it. A few minutes of resting time for the chicken, and dinner is ready to go straight from pan to plate.