Warm buttermilk to 110°F in microwave or on stovetop. Mix yeast with warm buttermilk and pinch of sugar in small bowl. Let sit 5 minutes until foamy and bubbly. If it doesn't foam, yeast is dead - start over with fresh yeast. This proves your yeast is alive and active.

In large bowl or stand mixer, combine melted butter, eggs, cocoa powder, red gel food coloring, vanilla, and salt. Mix until smooth and completely combined. Add the foamy yeast mixture and stir. The mixture will look very red at this point. Gradually add flour one cup at a time, mixing after each addition until dough forms.

Knead dough on floured surface for 8-10 minutes by hand or 5-6 minutes in stand mixer with dough hook. Dough should be smooth, elastic, and slightly sticky but not wet. If too sticky, add flour one tablespoon at a time. If too dry, add water one teaspoon at a time. Proper kneading develops gluten for soft fluffy texture.

Place dough in large greased bowl, turning once to coat all sides with oil. Cover with damp towel or plastic wrap. Let rise in warm spot 1-2 hours until doubled in size. Don't rush this step. Press finger into dough - if indent stays, it's ready. If it springs back, needs more time. Punch down dough gently to release air bubbles.

Turn dough onto floured surface. Roll into large rectangle about 15x10 inches and ¼ inch thick throughout. Use ruler to check dimensions if needed. Edges should be fairly straight and thickness even. Uneven rolling makes some rolls bigger than others after baking.

Spread softened butter all over dough surface leaving ½ inch border on one long edge. Mix brown sugar and cinnamon in small bowl until combined. Sprinkle cinnamon sugar mixture evenly over buttered dough. Press filling gently into butter with your hands so it sticks and doesn't fall out when rolling.

Starting from long edge opposite the border, roll dough up tightly like a log. Keep tension even as you roll - not too tight or too loose. Roll seam side down. Pinch seam to seal. Roll log back and forth gently to even out shape if needed.

Use unflavored dental floss or very sharp knife to cut log into 12 equal pieces about 1.5 inches thick each. For dental floss method, slide floss under log, cross ends over top, and pull tight to slice through cleanly without squishing. Wipe knife between cuts if using knife.

Arrange cut rolls in greased 9x13 inch baking dish with small space between each. They should almost touch but not quite. Cover loosely with towel or plastic wrap. Let rise in warm spot 30-45 minutes until puffy and touching each other. This second rise is crucial for soft fluffy texture. Don't skip it.

Preheat oven to 350°F. Bake risen rolls 25-28 minutes until set in center but still soft to touch. Don't overbake or they'll be dry. Edges will be lightly golden. Centers should look slightly underdone - they continue cooking after removing from oven. Let cool 5 minutes before frosting.

Beat softened cream cheese and butter with hand mixer until fluffy and smooth with no lumps. Add powdered sugar gradually, beating well after each addition. Mix in vanilla extract. Add heavy cream one tablespoon at a time until frosting reaches spreadable but thick consistency. Spread generously over warm rolls while they're still in pan. Frosting will melt slightly into crevices which is perfect. Serve warm.