Pat roast dry; season with salt and pepper. Heat oil in Dutch oven on medium-high heat. Add roast; brown well on all sides, 10 to
minutes. Remove roast from pan.
Add garlic and onion to pan. Reduce heat to medium; cook until lightly browned, about
to 4 minutes (NOTE: add splash of water to prevent scorching if needed). Stir in wine,
scraping up any browned bits from bottom of pan. Stir in soup, soaked dried mushrooms and reserved soaking liquid.
Transfer roast and any liquid from pan into a slow cooker insert. Cover and cook on LOW for 6 to 8 hours.
Remove roast to cutting board; keep warm. Add button mushrooms to sauce; cover and cook on HIGH for 30 minutes or until tender. Carve roast and serve with sauce.