In a saucepan, over medium-high heat, combine butter and flour to make a roux. When the roux comes together as a ball, add chicken broth and onions, stirring constantly. Add remaining sauce ingredients and heat it all together, stirring constantly. Remove from heat and set aside.
Preheat oven to 350 F. Mix filling ingredients and stuff cannelloni shells (do not precook shells). Pour a layer of sauce in a 9 x 13 pan. Add to the cannelloni to the pan. Coat cannelloni with remaining sauce.
Bake for 50 - 60 minutes. Broil for last 5 minutes.