Boil a large pot of salted water. Cook pasta until just shy of al dente. Reserve some cooking water and drain.
Heat olive oil in a wide skillet over medium-high. Brown the sliced chicken sausage until golden. Transfer to a plate.
Soften onion and bell pepper in the same skillet, scraping up browned bits. Stir in garlic and tomato paste; cook 1 minute.
Pour in crushed tomatoes and chicken broth. Simmer 5 to 7 minutes until slightly thickened.
Stir in half-and-half, Italian seasoning, red pepper flakes, salt, and black pepper. Warm through.
Fold in spinach to wilt. Return sausage to the pan and toss to coat.
Add drained pasta. Splash in reserved pasta water and toss until glossy and saucy.
Turn off heat. Stir in Parmesan and basil. Taste and adjust seasoning, then serve hot.