Place sausage and ground beef into a large saucepan over medium heat; cook and stir until meat is browned and crumbly, about 10 minutes. Break the meat apart as it cooks. Stir in mushrooms, 1 teaspoon salt, 1/2 teaspoon black pepper, Italian herb seasoning, and red pepper flakes. Turn heat to medium-high and cook until mushrooms have given off their juices and bottom of pan is almost dry.