Boil, mash, and cool a large sweet potato.
In a large mixing bowl or the bowl of a stand mixer, combine sweet potato puree, butter, sugar, eggs, and salt.
Stir in warm milk and yeast mixture (or add instant yeast with flour).
Add flour gradually, mixing with dough hook attachment until a soft dough forms.
Knead on a lightly floured work surface until smooth and elastic.
Place dough in a lightly greased bowl, cover with plastic wrap, and let rise in a warm place for 90 minutes.
Punch down risen dough, divide, and shape into rolls. Place in greased baking dish.
Brush with egg wash, cover, and let rise for 40–60 minutes.
Preheat oven to 375–390°F. Brush tops again with egg wash, sprinkle sea salt, and bake 20 minutes until golden brown.
Cool slightly on a wire rack before serving.