In a medium bowl, combine the water, yeast, and 1/2 teaspoon of granulated sugar. Stir and set aside to proof.
Microwave the butter until almost melted.
In the bowl of a stand mixer fitted with the hook attachment, add the remaining 1/3 cup of granulated sugar, flour, creamy mashed potatoes, salt, eggs, and butter. Turn the mixer on low and mix until combined.
Slowly add in the proofed yeast mixture and increase the mixer speed to medium. Mix until a smooth dough forms and it no longer sticks to the walls of the bowl.
Transfer dough to a large greased bowl and cover loosely with plastic wrap or a clean kitchen towel. Let it rise for 90 minutes in a dark and warm place, until almost doubled in size.
Grease a 9x13-inch baking pan with cooking spray or butter.
Roll the dough into 16 equal balls, and arrange in the greased baking pan, seam-side down.
Cover loosely with plastic wrap or a clean kitchen towel and allow to rise for 2 hours in a dark and warm place, but NOT on top of the oven.
Preheat oven to 350 degrees F.
Remove the plastic and bake for 20 to 25 minutes, or until the tops are golden brown.