Dissolve the yeast in the water. Put the 2 1/2 cups of biscuit mix in a large bowl; stir in the sugar. Add the yeast mixture, stirring vigorously. Sprinkle the work surface generously with the remaining 1/2 to 1 cup biscuit mix.
Turn the dough out onto the surface and knead well, 15 to 20 times. Shape the dough as desired. (I shape heaping tablespoons of dough into balls). Place on a lightly greased baking sheet, cover with a damp cloth, and let rise in a warm place for 1 hour.
Just before putting into oven, brush rolls with melted butter. Bake for 12 to 15 minutes, or until golden brown. Brush the rolls again with melted butter while they're hot.