1Spray 5- to 6-quart slow cooker with cooking spray. In medium bowl, mix ricotta cheese, 1/2 cup of the Parmesan cheese and the salt. In large bowl, mix Alfredo sauce and 4 teaspoons rosemary.
2In slow cooker, spread about 1 1/4 cups of the Alfredo sauce. Layer with 3 of the noodles (breaking as needed to fit), 1 cup of the chicken, one-third of the spinach, one-third of the tomatoes, one-third of the ricotta mixture and one-third of the cheese blend. Repeat layers twice. Sprinkle with remaining 1/2 cup Parmesan cheese.
3Cover; cook on Low heat setting 3 hours, rotating slow cooker insert halfway through cooking time, or until bubbly and noodles are tender. Turn off slow cooker. Let stand 15 minutes before serving. Garnish with additional rosemary.