Place chopped fresh spinach in a colander in sink. Cook penne pasta in boiling salted water according to package directions for al dente. Reserve 1 cup cooking water; drain pasta over spinach. Set aside.
Heat sun-dried tomato oil in stockpot over medium-high. Add sliced sun-dried tomatoes and chopped yellow onion; cook, stirring often, until tender, about 4 minutes. Add sliced garlic, leftover roasted garlic, kosher salt, and crushed red pepper; cook 1 minute.
Add heavy whipping cream; cook until reduced slightly, about 3 minutes.
Stir in pasta, spinach, grated Parmesan cheese, and shredded Roasted Lemon-Pepper Chicken. Stir to combine; add reserved pasta water gradually until pasta is saucy.
Season to taste with kosher salt; serve with additional Parmesan.
