In a large mixing bowl, combine mashed potatoes, milk, butter, sugar, and salt.
Sprinkle yeast over the mixture and let it sit for 5 minutes.
Gradually add flour, mixing until a soft dough forms.
Knead the dough on a floured surface for about 10 minutes.
Place the dough in a greased bowl, cover, and let rise until doubled, about 1 hour.
Preheat oven to 375°F (190°C).
Divide the dough into 12 pieces, shape into rolls, and place on a greased baking sheet.
Let the rolls rise for another 30 minutes.
Bake in the preheated oven for 20-25 minutes, or until golden brown.