In a medium saucepan bring buttermilk, water, sugar, butter, and salt just to boiling. (Mixture may appear curdled.) Remove from heat. Stir in potato flakes; let stand until temperature is 120F to 130F (about 15 minutes). Stir in snipped or dried sage.
In a large mixing bowl stir together 1-1/2 cups of the all-purpose flour and the yeast. Add potato mixture. Beat with an electric mixer on low to medium speed for 30 seconds, scraping sides of bowl constantly. Beat on high speed for 3 minutes. Using a wooden spoon, stir in as much of the remaining flour as you can.
Turn out dough onto a lightly floured surface. Knead in enough of the remaining flour to make a moderately stiff dough that is smooth and elastic (6 to 8 minutes total). Shape into a ball. Place in a lightly greased bowl; turn once to grease the surface of dough. Cover and let rise in a warm place until double in size (45 to 60 minutes).
Punch down dough. Turn out onto a lightly floured surface. Divide in half. Cover and let rest for 10 minutes. Grease 2 large baking sheets; set aside. Divide each half of the dough into 12 pieces. Shape pieces into balls. Arrange on prepared baking sheets about 2 inches apart. Loosely cover; let rise until nearly double in size (about 30 minutes).
Bake rolls in a 350F oven about 12 minutes or until golden. Remove rolls from baking sheets; cool slightly on wire racks. Serve warm. Makes 24 rolls.