Basic Roast (More Information)
Cooking a roast is pretty straightforward. It requires some liquid to cook the roast in, water will bring out more of the roast's own flavors but broth will introduce new flavors to the roast.
Once you've got the liquid, it then requires other ingredients that work will with the roast. If it is a pork roast, foods with heavier tastes will off set the lighter taste of the pork. This includes onions instead of leeks, since they are stronger, and sweet potatoes instead of potatoes, since sweet potatoes have a stronger flavor. For beef though, things that have a lighter flavor to better complement the flavor of the beef work well – such as potatoes, onions and carrots.
That is only the first condition. The second is selecting foods that taste better once allowed to cook for long periods of time. Potatoes are great when cooked for long periods of time; sweet potatoes are even better. Same goes for onions, celery and carrots – all of which will take on new flavors over long cooking periods. This requires a lot of experimentation to figure out what really works.
The biggest trick for the roast however is not the ingredients or the liquid – it is time. The longer this is in at a lower temperature, the more tender the meat will get. So start the roast in the morning, add in the extra ingredients at lunch time and by dinner time everything will taste perfect.

