Cook broccoli in boiling water to cover 5 minutes; drain.
While broccoli cooks, place flour in a Dutch oven or large saucepan. Gradually add broth, stirring with a whisk until blended. Bring to a boil, stirring with a whisk; reduce heat to medium, and cook 5 minutes or until mixture thickens. Add butter, stirring with a whisk until melted. Add Parmesan cheese, next 4 ingredients (through pepper), and 1/2 cup cheddar cheese, stirring until cheeses melt. Stir in broccoli, rice, and chicken.
Spoon rice mixture into a 9-inch square glass or ceramic baking dish coated with cooking spray. Top with remaining cheddar cheese, and sprinkle with almonds. Cover and bake at 375° for 20 minutes. Uncover and bake 15 additional minutes or until bubbly and top is browned.