Some people swear by adding the carrots and potatoes halfway through the cooking time. I am not a fan of that option because I like to walk away from my Crock Pot pot roast for the rest of the day. Instead I cut the potatoes into large 2-inch chunks and place them on top of the roast. That way, the roast is closest to the heating elements, which is more important than the vegetables. Put the vegetables around and on top of the roast. After 8-10 hours on low, the roast will be fall apart soft and the vegetable will be perfectly fork tender.