Preheat oven to 375ºF. Coat beets in 1 tablespoon of olive oil; wrap in aluminum foil. Place on a baking sheet and bake for 30 minutes. Leave oven on.
Carefully unwrap beet and let stand until cool enough to handle. Gently rub with a towel to remove skin from beets. Place beets in a blender.
Add garbanzo bean flour, remaining 2 tablespoons of oil, horseradish and salt to blender; blend until smooth.
Form mixture into 1-inch-thick, 4-inch wide patties. Place patties on the same baking sheet and bake for 15 to 20 minutes, until crispy and cooked through. Enjoy on a salad, alone or on a bun. Store leftovers in the fridge; best if eaten within 24-48 hours.