Pre-heat oven to 400 F.
Trim off leafy beet tops and wrap the beets in foil and place on a baking sheet.
Roast the beets in the oven for about 1 hour, or until they are easily pierced with the tip of a knife.
Remove the beets from the oven and let them cool in the foil.
Unwrap the foil and then peel the beets and then cut into bite-sized cubes.
Meanwhile, place the potatoes in a pot with salted water, covering them by about 1 inch.
Bring to a boil over high heat, then reduce the heat to medium-low, cover, and simmer until the potatoes are tender when pierced with a knife, about 15 minutes. Drain and set aside. Once cool enough to handle, peel them, if desired. If necessary, you may need to cube the larger potatoes.
In a serving bowl, stir together the sour cream, mayonnaise, horseradish, 2 tbsp dill, and healthy pinches of salt and pepper.
Fold the beets and potatoes into the dill dressing.
Cover and refrigerate for at least 20 minutes or up to 24 hours. When ready to serve, garnish will fresh chopped dill.