Bring a large pot of well-salted water to a boil. Cook rotini or penne until al dente, about 8 to 10 minutes. Pasta should be tender but firm enough to hold its shape.

While pasta cooks, whisk together Caesar dressing, lemon juice, olive oil, garlic powder, anchovy paste if using, salt, and pepper in a small bowl until smooth.

Drain pasta and rinse briefly under cold water. Shake off excess water and transfer to a large mixing bowl. Pour half the dressing over the warm pasta and toss to coat. Let sit for 5 minutes.

Add diced chicken, halved cherry tomatoes, grated Parmesan, and parsley if using. Toss gently to combine.

Right before serving, fold in the chopped romaine and most of the croutons, reserving a handful for topping. If the salad looks dry, add remaining dressing one tablespoon at a time. Taste and adjust seasoning. Top with reserved croutons and extra Parmesan. Serve chilled or at room temperature.