Rub roast with 1 teaspoon fresh ground pepper. In a Dutch oven (or large pot), heat olive oil over medium-high heat. Sear the roast, flipping on all sides until well browned (about 10 minutes).
To the pot add wine, parsley, thyme, salt if using, remaining 1 teaspoon of pepper, garlic cloves, onion, carrots, potatoes, and celery. Pour tomatoes over top.
Cover and bake for 3½ hours. Check for doneness by using a fork to see if the meat shreds easily and is tender. If the meat is not tender, bake for 30 more minutes.
Remove from oven, remove thyme sprigs, and place meat on a cutting board. Put vegetables in a dish and cover (if thickening gravy).
Pull meat with two forks, or slice against the grain. Serve with vegetables and juices or gravy.
To thicken gravy, place the Dutch oven on medium-high heat and bring the liquid to a boil. Meanwhile, mix the cornstarch and water slurry together and set aside. Once the liquid has reached a boil, stir the slurry and add about half to the liquid, whisking to thicken. Add more slurry until gravy reaches desired consistency.
Notes
*not large baby potatoes, they will get mushy
**Use 1 can for a more traditional pot roast. Use 2 cans for more of a tomato sauce. The additional liquid is also helpful for braising. You may not need the full 2 cans, but up to 2 cans can be used if your pot size allows for it.