I am basic-cooking challenged. I really want to cook a roast tonight using my DCB. I have onions, potatoes and carrots all ready. 1. What kind of roast do I buy? How do I know how to pick one out?? 2. What exactly do I do with it? Haha broad questions I know but I don't know how to do this and I'd really like to learn! thanks in advance for any help!