Preheat oven to 450°.
. Place sweet potatoes on a foil lined baking sheet; bake at 450° for 1 hour or until tender. Cut potatoes in half lengthwise; cool to touch.
. While potatoes cool, dissolve yeast and 1 teaspoon brown sugar in warm water in a large bowl; let stand 5 minutes. Add milk and next 4 ingredients, stirring until sugar dissolves. Add egg; stir well.
. Peel and mash sweet potatoes with a fork until smooth. Stir 1 1/2 cups potato into yeast mixture. Reserve remaining potato for another use.
. Lightly spoon flour into dry measuring cups; level with a knife. Add 2 cups flour to yeast mixture; stir until smooth. Gradually stir in enough remaining flour to form a soft dough. Turn dough out onto a lightly floured surface. Knead until smooth and elastic (about 8 minutes), adding just enough remaining flour to prevent dough from sticking.
. Place dough in a large bowl coated with cooking spray, turning to coat top. Cover with plastic wrap, and let rise in refrigerator at least 8 hours or up to 3 days, punching dough down as necessary when dough rises to top of bowl.
. Coat 3 (9-inch) round cake pans with cooking spray. With lightly floured hands, shape dough into 36 (1 1/2-inch) balls. Place 12 balls in each pan, making sure balls do not touch. Cover and let rise in a warm place (85°), free from drafts, 45 minutes or until doubled in size. (Press two fingers into dough. If indentation remains, the dough has risen enough.)
. Preheat oven to 375°.
. Uncover rolls, and bake at 375° for 15 to 18 minutes or until golden.
10. Combine 1 tablespoon butter, 1 teaspoon orange rind, and 1 tablespoon orange juice. Brush over warm rolls in pan. Serve warm.