Sprinkle yeast and sugar onto warm water. Stir to dissolve. Let stand until yeast bubbles form, about 5 minutes. Pour into large mixing bowl.
Stir in butter, sugar, warm milk and salt.
Add in mashed potatoes, eggs and 3 cups flour. Stir until dough becomes thick and hard to mix.
Knead dough adding in more flour as needed until dough is slightly sticky but won't stick to your hands (for me, its between 4 1/2-5 cups).
Grease large bowl with a little oil or melted butter, place dough into bowl and cover with plastic wrap. Let rise for 1-1 1/2 hours until doubled in size.
Punch down dough and divide into 24 equal pieces. Roll into small balls and place into greased glass baking dishes. Cover rolls with plastic wrap and let rise another 1-1 1/2 hours until doubled in size.
Preheat oven to 400 degrees and bake rolls 15 minutes (except, check them after 10!) Rolls are best served warm, but are still great at room temperature. Store in air tight containers.