In a mixing bowl, whisk together 2 tablespoons olive oil, Italian seasoning, minced garlic, chopped parsley, lemon juice, salt, and pepper. Add chicken breasts and turn to coat thoroughly. Marinate for at least 10 minutes at room temperature, or cover and refrigerate up to 2 hours.

Preheat oven to 400°F (200°C). Toss halved baby potatoes with 1 tablespoon olive oil, garlic powder, smoked paprika, salt, and pepper. Spread in single layer on rimmed baking sheet, cut side down. Roast for 20 to 25 minutes, flipping halfway through, until golden brown and fork-tender. Sprinkle with fresh parsley when done.

Bring medium pot of salted water to rolling boil. Add penne and cook until al dente, 9 to 11 minutes. Reserve ¼ cup pasta water before draining. Drain pasta in colander.

Return pot to medium heat. Add heavy cream and warm for 1 minute. Stir in pesto sauce and grated Parmesan until smooth and creamy, about 2 minutes. If too thick, add reserved pasta water 1 tablespoon at a time. Toss in cooked penne and fresh herbs until coated. Adjust seasoning.

Heat grill or grill pan over medium-high heat (375-400°F). Lightly oil grates. Remove chicken from marinade and place on hot grill. Cook for 5 to 7 minutes per side without moving, until internal temperature reaches 165°F. Transfer to cutting board and rest for 5 minutes, then slice against the grain.

Divide creamy pesto pasta among shallow bowls or plates. Arrange roasted potatoes alongside pasta, then top with sliced grilled chicken. Garnish with extra fresh herbs, lemon wedge, or Parmesan cheese.