Spray 3 1/2- to 4-quart slow cooker with cooking spray. Mix chicken, sausage, bell pepper, onions, garlic, oregano, pepper flakes, tomatoes and tomato paste in slow cooker. Cover; cook on Low heat setting 6 to 8 hours.
About 25 minutes before serving, cook rice in 2 cups water as directed on package.
Just before serving, stir artichoke hearts and olives into chicken mixture. Cover; cook until hot. Serve chicken mixture with rice.