Combine yeast, 1 teaspoon sugar, and warm water; stir well, and let stand 5 minutes or until bubbly.
Combine milk and butter in a large bowl, stirring until butter melts. Add 2/3 cup sugar, eggs, and salt, stirring well. Stir in yeast mixture and enough flour to make a soft dough. Place in a greased bowl, turning to grease top. Cover and let rise in a warm place (85°), free from drafts, 1 hour or until doubled in bulk.
Turn dough out onto a lightly floured surface; divide in half. Roll each half into a 20- x 8-inch rectangle; brush with melted butter, leaving a 1-inch margin on all sides. Combine 2 cups sugar, brown sugar, and cinnamon; sprinkle evenly over each rectangle of dough.
Roll each half up jellyroll fashion, beginning at long side; moisten edges with water to seal. Cut rolls into 1-inch slices; place slices, cut side down, in a greased 15- x 10- x 1-inch jellyroll pan. Cover and repeat rising procedure 1 hour or until doubled in bulk. Bake at 375° for 20 minutes or until lightly browned.