Preheat oven to 425. Use 1 tablespoon softened butter to grease the bottom and sides of a 9 inch cake pan. Set aide.
In a medium bowl combine sugar, brown sugar, cinnamon, salt and vanilla. Mix together and set aside.
In a large bowl whisk together flour, sugar, baking powder, baking soda, and salt. Using a liquid measuring cup, measure 1 cup of buttermilk, add 1/4 cup other milk (I used 1%) and then whisk in 2 Tbs melted butter. Mix buttermilk mixture into dry ingredients until just combined, then knead with well-floured hands for about 30 seconds, sprinkling in a little extra flour as needed if dough is too sticky to work with.
Generously flour a clean work surface. Roll (or press with fingertips) dough into a 12x10 inch rectangle. (does not have to be exact). Brush 2 tablespoons softened butter onto the entire surface of the dough. Sprinkle brown sugar filling evenly onto dough coming to about 1/2 inch of edges.
Lightly press filling into dough. If including optional raisins, now sprinkle them on top of the dough. Starting with the long end of the rectangle, roll the dough to the opposite end. Pinch to seal along the length of the rolls to seal the filling in. Pinch the ends together and cut off the excess, about 1/2 inch. Cut the dough into 8 equal sections.
Place one roll in the middle of the buttered cake pan and then place the remaining seven rolls evenly around the first. Brush the tops with remaining 2 Tbs melted butter.
Place rolls in the oven and allow to bake at 425 for about 15 minutes, then reduce temperature to 350 and allow to bake about 10 more minutes, until edges begin to lightly brown. (I like mine a little more doughy so I pulled them out a little early.)
While rolls are baking, prepare the frosting. Using a hand mixer, beat softened butter and cream cheese until light and creamy. Add in powdered sugar, vanilla, and milk. Mix until well combined. When rolls are finished baking, allow to cool 5-10 minutes before spreading the frosting on. Store in airtight container for 2 days or serve immediately.