Combine the buttermilk and butter in a measuring cup.
In a large bowl or the bowl of a stand mixer, combine the flour, sugar, yeast, and salt. With the mixer on low speed, add the buttermilk mixture and eggs, and mix until the dough comes together.
Knead until smooth and elastic. If the dough is too stick add more flour, 1 tablespoon at a time, until the dough pulls away from the sides of the bowl and is slightly sticky to the touch.
Cover and let rise 2 - 2 1/2 hours, or until doubled in size.
When the dough has risen, grease or line with parchment paper a 9 x 13 baking dish.
Punch the dough down and press it into a 12 x 16 inch rectangle.
Brush the 1/2 cup butter over the dough, leaving a 1/2 inch border on all sides. Sprinkle the brown sugar and cinnamon over the dough, pushing the sugar mixture gently into the dough with your hands.
Roll the dough into a tight log, seam side down. Cut the dough into twelve even sized rolls using a serrated knife.
Place cut side down in prepared baking dish.
Cover and let rise 1 - 1 1/2 hours, until doubled.
While the dough is rising, preheat the oven to 350 degrees. Bake the rolls for 22-25 minutes, until lightly golden and cooked through. Remove and let cool for a few minutes.
Whisk together the powdered sugar, cream cheese, milk, and vanilla, and drizzle it over the warm rolls. Enjoy!