Place the yeast and warm water in a bowl or container, stir once, and let rest.
Add the milk and buttermilk to a microwave-safe container and heat until warmed. It is okay if the buttermilk separates at this point; it will not affect the recipe.
Stir 2 tbsp softened butter into the milk and buttermilk mixture until melted.
In a mixing bowl, combine the milk mixture, yeast, granulated sugar, salt, and 1 cup of flour. Beat on high with a dough hook until well combined and smooth.
Add the egg to the bowl and beat until well incorporated.
Gradually add the remaining flour, a little at a time, until the dough comes cleanly away from the dough hook attachment in the mixer.
Lightly flour the dough and shape it into a ball in a well-greased large mixing bowl.
Cover and let the dough rise for 1 hour.
Place the dough onto a floured surface and roll it out until it is 1/2 inch thick.
Cut the dough into 12 even rectangular shapes.
Fold the ends of each rectangle under to form a roll shape and place on a parchment or silicone mat-lined baking sheet. Allow them to rise slightly for 20 minutes.
Preheat the oven to 400°F.
Bake the rolls for 12-15 minutes until lightly browned on top.
Brush the tops with melted butter if desired.
Combine the ingredients for the honey cinnamon butter in a bowl and mix until well combined.
Serve the warm rolls with the honey cinnamon butter.