In a large mixing bowl, combine warm milk, sugar, and yeast. Let it sit for 5 minutes until frothy.
Add mashed potatoes, melted butter, and salt to the yeast mixture. Mix well.
Gradually add flour to the mixture, stirring until a soft dough forms.
Turn the dough onto a floured surface and knead for about 10 minutes until smooth and elastic.
Place the dough in a greased bowl, cover, and let it rise in a warm place for about 1 hour or until doubled in size.
Preheat the oven to 375°F (190°C).
Punch down the dough and divide it into 12 equal pieces. Shape each piece into a roll and place on a greased baking sheet.
Cover the rolls and let them rise for another 30 minutes.
Bake in the preheated oven for 20-25 minutes or until golden brown.