What is a pot roast?
In Britain that would be a fairly cheap cut of meat that is put into casserole or crock pot and roasted slow for several hours to tenderise the meat. You could also add vegetable to it or just onions.
In my neck of the woods, pot roast is a 3 or 4 lb. chuck roast (you can't go wrong with that cut). You cut off the fat, roll in flour if desired, sear on all sides in hot oil, then add 1/2 C. water, salt, and pepper, and roast, covered, in the oven for 2-1/2 to 3 hours, adding vegetables (usually potatoes, onions, and carrots) during the last 90 minutes or so.
The juices make a fantastic gravy.