Bring a large pot of salted water to a boil and cook pasta according to package directions until al dente. Drain and rinse under cold water, then let cool completely. In a large bowl, combine cooled pasta and diced chicken. Add Caesar dressing, garlic powder, black pepper, and lemon juice. Toss until evenly coated. Fold in chopped romaine and grated Parmesan cheese gently. Just before serving, add croutons and toss lightly to maintain crunch. Taste and adjust seasoning if needed.