Fill a large pot with lightly salted water and bring to a rolling boil. Stir in rotelle and return to a boil. Cook rotelle uncovered, stirring occasionally, until tender yet firm to the bite, 8 to 10 minutes; drain.

Preheat the oven to 350 degrees F (175 degrees C).

Cook bacon in a large, deep skillet over medium-high heat until evenly browned; transfer to a paper-towel-lined plate. Stir onions into skillet; cook until translucent.

Melt butter in a separate pan. Add mushrooms; sauté.

Combine rotelle, bacon, onions, mushrooms, soup, and sauerkraut; season with salt and pepper. Pour into a 9x13-inch baking dish.