Mix the wet ingredients: In the bowl of a stand mixer, whisk together warm buttermilk, sugar, melted butter, egg, and food coloring.
Make the dough: Add yeast, cocoa powder, salt, and 2 cups of flour. Mix on low. Gradually add remaining flour until a soft dough forms.
Knead: Switch to the dough hook and knead on medium-low for 5-7 minutes until the dough is smooth and tacky but not sticky.
First rise: Place dough in a greased bowl, cover, and let rise in a warm place for 60-90 minutes or until doubled in size.
Roll and fill: Roll dough into a 12x18 inch rectangle. Spread softened butter over the surface. Whisk brown sugar and cinnamon together, then sprinkle evenly over the butter.
Cut and second rise: Roll the dough into a tight log. Cut into 12 rolls using dental floss or a sharp knife. Place in a greased 9x13 pan. Cover and let rise for 30-45 minutes.
Bake: Preheat oven to 350°F (175°C). Bake rolls for 20-25 minutes until centers spring back when touched.
Frost: Beat cream cheese, butter, powdered sugar, and vanilla until fluffy. Spread over warm rolls.
