Combine 2 cups flour, undissolved yeast, sugars, salt and orange peel in a large mixer bowl. Heat water, buttermilk and butter until very warm (120° to 130°F) and add to bowl. Add sweet potato and egg; beat on high for 3 minutes. Stir in enough flour to form a soft dough. Knead on a lightly floured surface for 8 to 10 minutes until smooth and elastic. Cover and let rest for 10 minutes.
To prepare the filling: Combine brown sugar and cinnamon in a small bowl. Stir in pecans.
To prepare the topping: Mix together powdered sugar, butter, egg white and corn syrup until smooth. Stir in pecans.
Roll dough into a 10 x 18-inch rectangle. Spread evenly with butter. Sprinkle brown sugar mixture over butter leaving a 1-inch border on the long edges. Roll up dough starting at one long side, like a jelly-roll. Place the roll seam side down. Cut roll into 12 equal slices and place in a greased 13 x 9-inch baking pan. Evenly spread topping over rolls. Cover and let rise in a warm, draft-free place for 45 to 60 minutes, or until doubled in size.
Bake in a preheated 350°F oven for 30 to 35 minutes, or until golden brown. Let rolls cool for 5 minutes. Stir together glaze ingredients until smooth, drizzle evenly over rolls.
Make Ahead Directions: After rolls have been placed in baking pan, cover with plastic wrap sprayed with nonstick spray. Refrigerate for 12 to 24 hours. Remove and let stand 30 minutes. Bake as above.