How to Make It
Preheat oven to 400°F. Place beets, potatoes, and 1 cup water in a 13- by-9-inch baking dish. Drizzle with 2 tablespoons oil and season with ½ teaspoon salt and several grinds of pepper. Cover with aluminum foil and roast until beets and potatoes are tender when pierced with a small sharp knife, 45 to 55 minutes. Uncover and set aside until cool enough to handle, about 15 minutes.
Peel cooled beets, slice into wedges, and transfer to a large bowl. Using your hands, gently crush potatoes into bite-size pieces and add to beets.
Cook bacon in a large skillet over medium, turning occasionally, until crisp, 5 to 7 minutes. Drain on a paper towel–lined plate and let cool 5 minutes. Break or chop into pieces and add to beets and potatoes.
Whisk together vinegar, mustard, shallot, remaining 2 tablespoons oil, remaining ￼½ teaspoon salt, and several grinds of pepper in a small bowl. Pour dressing over beet mixture and toss to combine. Serve at room temperature.