Can you cook a pot roast without using a pot or a crock pot?

Yes. You can cook your roast in a baking tray, but it has to be deep enough to hold the juices that will come out of the roast during cooking. And it would need to be put in the oven, not on a burner. Depending on how big your roast is, I'd say about at least 2 or 3 inches deep for it. If you don't want to fork over a lot of money on a pot, you can buy those aluminum roasting pans in your local grocery store or Walmart for just a few bucks. They can be re-used if you handle them with care, just wash them and be careful not to bend them all out of shape. Some of them even come with plastic lids, but you can't put the lids in the oven.