You would cook it as a normal roast i.e basting every once in a while and the like. With pork I find that if you slow roast it it is much more tender. Also with marinade meats they tend to be tender already so I dont roast them in the oven, I have an electric frypan that I do them in then after the meat is done and I take out the juices for gravy, I cook my veges ( with the potatoes I par boil them before hand) in the frypan. If you wanted to do them in the oven though par boil potatoes, when they have cooled a bit pop them in a bowl with carrot pieces and add a bit of melted butter, black pepper and thyme. Roast until golden brown in a 210-220degree oven. I found better results in a ceramic dish for roasting veges too.

Sorry not sure about tomatoes, I've never done them before.