Prep proteins: Season chicken with salt, pepper, paprika, and half of the Cajun seasoning.
Brown sausage (optional): In a skillet, sauté sausage slices in olive oil for 2–3 minutes, then transfer to slow cooker.
Add vegetables: Add onion, bell pepper, celery, and garlic to the slow cooker.
Add liquids and seasonings: Stir in diced tomatoes, chicken broth, remaining Cajun seasoning, thyme, oregano, cayenne pepper, and rice.
Add chicken: Place seasoned chicken in the slow cooker. Stir to combine.
Slow cook: Cover and cook on low for 4–5 hours or high for 2–3 hours until chicken and rice are cooked and tender.
Add shrimp: About 20–25 minutes before serving, add shrimp and stir gently. Cover and cook until shrimp are pink and opaque.
Serve: Garnish with chopped parsley and green onions. Serve hot.