Pat the roast dry with paper towels then season with salt and pepper. Heat the oil in the bottom of a large Dutch oven over medium-high heat.
Place the seasoned roast in the pan and brown the roast on all sides. Remove and place on a plate.
If needed, add more oil, then sauté the mushrooms and onions for 5-6 minutes to release some of their moisture. Add in the garlic and sauté for another 4 minutes.
Slowly pour in the broth, scraping any browned bits off of the bottom of the pot. Stir in the onion soup mix.
Place the roast back into the middle of the Dutch oven, then add in the carrots and potatoes, placing around the roast.
Cover and cook for approximately 1 1/2 hours (30 minutes per pound). Bring the internal temperature to 135°F (for medium rare meat), 145°F (for medium meat), or 150°F (for medium well).
Transfer the roast, carrots, and potatoes to a warm platter and lightly cover with aluminum foil to keep warm. Heat the drippings on the stove top in the Dutch oven.
Combine cornstarch and cold water until smooth. Whisk into the drippings and cook until thickened.
To serve, slice the meat, and serve it with the vegetables and gravy.
Notes
When cooking a roast for a long time, the larger you cut your vegetables the less mushy they will be!
The cooking time will vary depending on the thickness of the roast, etc.