I have two favorite ways to cook any type of roast.
The first is to use a Reynold's roasting bag and just follow the instructions within the package. You can actually purchase a box of roasting bags and check the instructions while in-store to make sure you have all ingredients on hand to make your meal. The roasting bags make a very moist and delicious roast every time with minimal effort!
My second choice for cooking a roast is to place it in a large crock pot slow cooker with some spices (use your favorites or just pour an envelope of dry onion soup mix on top and add about a 1/2 cup of water). I set the dial to low and let it cook ALL DAY on low. It makes my home smell wonderful and is another great, easy way to make dinner. I will even go so far as to use the meat drippings from the crock pot to make gravy on a good day! :)
You can actually bake your potatoes with your roast in the crock pot too! Just wash them well and pat dry. Wrap each in it's own piece of aluminum foil and place in bottom of crock pot. Place roast on top and cook on low for 8 hours or on high for 5-7 hours. A great step by step recipe for stacking this meal in the crock pot can be found on Stephanie O'dea's wonderful crock pot website here.