Preheat oven to 425 degrees F (220 degrees C). Wrap beets in aluminum foil and place in a baking dish.
Roast beets in the preheated oven until tender, about 45 minutes. Remove from foil and cool completely. Peel cooled beets and cut into 1/4-inch slices.
Cook and stir sunflower seeds in a skillet over medium heat until fragrant and toasted, 2 to 5 minutes. Cool completely.
Whisk olive oil, vinegar, onion, salt, black pepper, and sugar together in a bowl until dressing is thick and creamy.
Stir beets, sunflower seeds, and sunflower sprouts together in a bowl; drizzle dressing over the top and toss to coat.
