Making a pot roast, what do I do?

My boyfriend brings home giant pork roasts from his job. The best way I have found to cook them is I throw the roast in an oven roaster pan with a little water in the bottom. Then I sprinkle it with Season salt pepper onion powder, garlic salt, and rosemary and put it in the oven at 350 until there is about an hour left on the cook time ( I cook the meat an hour per pound) then I add all of the cut up veggies(carrots, potatoes, celery) and sprinkle it with rosemary again and serve it an hour later.