If you want to simplify this recipe even more, prep your vegetables, place them on a sheet pan, drizzle them with a little olive oil and roast them in the oven at 375° F during the last 30 minutes of cooking the corned beef. If you do that, add the cabbage in with the corned beef about 10 minutes before the roast is done and then remove the corned beef to a cutting board and cover it loosely with foil and let the corned beef rest for 10 minutes before carving. If you time it right it will all come out at the same time and it will be a great show.