Throw everything in crockpot except sour cream. Cook 8-10 hours in crockpot. Once done place strainer in a skillet and dump entire crockpot into strainer so that the juice goes into the skillet. Return roast and vegetables to crockpot. Simmer the juice over medium high heat to reduce for gravy. Once reduced to about half add in the sour cream with a whisk. Simmer to remove as many lumps as possible. Return gravy to crockpot and cook for an additional 20-30 minutes.