Combine flour, sugar, salt, and yeast in a large bowl.
Add warm water and melted butter, and mix into dough.
Knead on a floured surface for 10 minutes until smooth.
Place in a greased bowl, cover, and let rise for 1 hour.
Preheat the oven to 400°F (200°C).
Divide dough into 12 pieces, and shape into rolls.
Place rolls on a parchment-lined baking sheet.
Beat egg yolk, brush over rolls. Add sesame seeds if desired.
Bake for about 15-20 minutes until golden brown.
Cool on a wire rack before serving.
Enjoy your homemade Ozzie rolls!