Pierce brats with a fork several times. Place in pan and cover with beer. Bring to a boil and then simmer for 10 minutes. Remove brats from pan and pat.
Mix together the maple, mustard, mustard, oil, garlic and salt and pepper together.
Place potatoes, cabbage, onions, and brats on a sheet pan. Drizzle with mustard dressing and toss to coat. Spread out in even layer.
Roast for 35-40 minutes, or until cabbage is browned and potatoes are cooked through.
If you want this dish to remain Gluten-Free, do NOT boil your bratwurst in beer prior to roasting.
If you opt to par-boil your brats before roasting, I recommend selecting a German lager, such as Sam Adams Oktoberfest for the most flavor. If you are opposed to using beer, you can par-boil in apple cider or chicken stock which also imparts delicious flavor.
You can use any type of Bratwurst you like--Turkey, Chicken, Beef, or Pork.
If you don't have new potatoes, use red potatoes or even russet potatoes, cut into fourths.