Cook creamed spinach according to package directions; set aside.
. While spinach cooks, place flour in a small bowl; gradually add milk, stirring with a whisk until well blended. Melt butter in a medium saucepan over medium heat. Add milk mixture, stirring constantly with a whisk. Cook 5 minutes or until mixture begins to thicken. Remove from heat. Add cheese; stir until cheese melts.
. Stir in creamed spinach, chopped spinach, and tomatoes. Bring to a simmer over medium-low heat, and cook 5 minutes or until thoroughly heated.