Heat the canola oil in an oven-proof Dutch oven with lid over medium-high heat. Brown the roast on all sides, about 10 minutes total; remove from the heat. Pour in the cider. Sprinkle with the oregano, marjoram, thyme, salt, and pepper. Arrange the onion slices on the roast.
Replace the cover and bake in the preheated oven for 1 1/2 hours. Add the potatoes, carrots, onions and mushrooms. Pour in additional water if the roast looks dry. Continue baking covered until the roast pulls apart easily with a fork, about 1 1/2 hours longer.