Combine all dough ingredients (milk through pumpkin pie spice) in the bowl of a stand mixer fitted with a dough hook*. With the mixer on low speed, slowly add 1 Tablespoon of melted butter. Mix until a shaggy dough forms.
Transfer the dough to a smooth work surface and knead until a smooth dough forms, about 3-4 minutes. The dough should be smooth, soft and slightly tacky, but not sticky. If needed, add more flour or milk (1 Tablespoon at a time) to reach your desired consistency.
Transfer the dough to a large, oiled bowl and cover with plastic wrap. Let rise for 90 minutes, or until doubled in size.
Brush a 9x9-inch baking pan with 1 Tablespoon of melted butter and set aside.
Turn the dough onto a smooth work surface and divide into 9 equal-sized pieces. This doesn't have to be exact, but if you do want perfectly identical rolls, weigh the dough and divide that number by 9 to determine how much the dough for each roll should weigh. Mine were about 95g each. Using one palm for friction, roll each piece of dough into a ball with the seam side against your palm. Place the rolls into the prepared baking pan. Repeat until you have 9 rolls.
Cover the baking pan with plastic wrap and let rise for 60 minutes, until the rolls are puffed and doubled in size.
Preheat the oven to 375℉. Brush the rolls with 1 Tablespoon melted butter. Bake for 20-25 minutes until golden brown.
While the rolls bake, melt 2 Tablespoons butter for the topping in a small saucepan over low heat. Increase heat to medium-low and add the chopped sage. Let the butter simmer, swirling the pan occasionally, until the butter starts to brown (about 3 minutes). Remove from heat.
Remove the rolls from the oven and immediately brush with the browned butter and sage mixture. Sprinkle with flaky sea salt and serve while warm.
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Notes
*You do not need to use a stand mixer to make this recipe. You can also make the dough in a large bowl with a wooden spoon, and knead by hand. To make this recipe with active sourdough starter, omit the yeast and replace the sourdough discard with active starter (200g). You will also need to increase the rise times.