Soften the yeast in warm water and stir in the sugar and salt to dissolve. In a bowl, beat 2 of the eggs and blend in the flour. Then stir in the yeast mixture and melted butter. Knead vigorously in the bowl with the hands till the dough leaves the sides of the bowl and is elastic, about 5 minutes.
Make into a ball, put in a buttered bowl, and cover with plastic wrap. Let rise in a warm, draft-free place for 1 1/2 hours, or until doubled in bulk. Punch down and divide into 18 equal pieces. Roll the pieces into balls and arrange, well separated, on a buttered baking sheet.
Let rise 30 minutes, or until doubled in size. Brush with the remaining egg beaten with a teaspoon of water. Bake in a preheated oven at 375° for 10 minutes, or until nicely browned. Cool on a rack.