Heat potato water until warm (100º to 110ºF). Add yeast and allow to rest for 5 minutes.
Combine sour cream, mashed potatoes, eggs, sugar, salt and yeast mixture in a large mixer bowl. Gradually stir in enough flour to form a soft dough.
Knead dough on a lightly floured surface for 6 to 8 minutes, until dough is smooth and elastic. Shape dough into a ball and place in a greased bowl, turning once to cover. Cover and let rise in a warm, draft-free place until dough is doubled in size, about 1 hour.
Roll dough into an 18 x 12-inch rectangle. Brush with butter. Combine brown sugar, coffee and cinnamon; sprinkle over dough to within 1/2 inch of edges.
Roll up dough starting with the short end. Pinch seam to seal. Cut dough into 12 equal sized rolls. Place rolls, cut side down, in a greased 9 x 13-inch baking pan. Cover and let rise until doubled, about 30 to 40 minutes.
Bake for 25 to 28 minutes or until golden brown, in a preheated 350ºF oven. Cool pan on wire rack.
Mix powdered sugar, butter, cappuccino, vanilla and milk in a small bowl until smooth. Spread over warm rolls.
Recipe Tip - Use instant mashed potatoes prepared without butter or salt in place of cooking and mashing fresh potatoes.