Dissolve yeast in warm water; set aside.
Combine sugar, shortening, and milk in a medium saucepan; place over medium heat, stirring until shortening melts. Cool to 105 to 115 degrees.
Combine milk mixture and yeast mixture in a large mixing bowl; mix well. Add 5 cups flour; stir well. Cover and let rise in a warm place (85 degrees),free from drafts, 2 hours or until doubled in bulk.
Combine remaining 2 cups flour, salt, baking soda, and baking powder; mix well. Punch dough down, and stir in flour mixture. Knead dough until smooth and elastic (about 8 to 10 minutes). Place in a well-greased bowl, turning to grease top. Cover and refrigerate until needed.
Punch dough down, and divide into fourths. Roll each fourth into a circle about 23 inches in diametere and 1/4 inch thick; cut into 10 wedges. Roll each wedge tightly, beginning at wide end.
Place rolls on greased baking sheets, point side down; curve into crescent shpe. Cover and let rise in a warm place (85 degrees), free from drafts, 1-1/2 hours or until doubled in bulk. Bake at 400 degrees for 10 minutes or until lighly browned.