Prepare Dough: Dissolve Yeast In Warm Water In A Large Bowl. Stir In Milk, Sugar, Oil, Baking Powder, Salt, Egg, And 3 Cups Flour. Beat Until Smooth. Stir In Enough Flour To Make Dough Easy To Handle. Turn Dough Onto A Well Floured Surface And Knead Until Smooth And Elastic, 8 To 10 Minutes. Place In A Greased Bowl And Turn To Coat Top. Cover And Let Rise Until Doubled In Size, About 1 1/2 Hours. Punch Down And Divide In Half. Roll Each Half Into A 12" X 10" Rectangle. Spread With Half The Margarine. Combine Cinnamon And Sugar And Sprinkle Over The Margarine. Roll Up From Long Side And Pinch Edges To Seal. Stretch Roll Slightly To Make Even Thickness. Repeat With Other Half. Cut Each Roll Into 12 Slices. Place Slightly Apart In Two Greased 9" X 13" X 2" Pans. Wrap Each Pan Tightly With Aluminum Foil. Refrigerate For At Least 12 Hours But No More Than 48 Hours. Preheat Oven To 350 Deg F. Remove Foil From Pans. Bake Until Golden In Color, 35 To 40 Minutes. While Roll Bake Prepare Frosting. Combine Powdered Sugar, Milk, And Vanilla. Beat Until Smooth. Frost Rolls While Still Warm.