Heat 2 Tbsp butter over medium high heat in a saute pan.
Rub ranch seasoning into all sides of the roast. When butter begins to bubble, add the roast to the pan. Brown on both sides.*
Transfer the browned roast to the slow cooker. Pour beef stock into the saute pan and stir with a wooden spoon to get all those delicious brown bits. Pour the stock over the roast in the slow cooker.
Place remaining 4 Tbsp butter on top of the roast.
If using Pepperoncini peppers, place them around the roast in the slow cooker.
Cook on low for 8 hrs (or high for 2 hrs, then on low for 4 hrs).
If using potatoes and carrots, add them during the last 4 hours of cooking.
To serve, ladle the juices over the roast and sprinkle with parsley.
Store leftovers in the fridge - makes great roast sandwiches the next day!