Heat a 10-inch saute pan over medium heat. Add the oats and cook, stirring occasionally, until toasted, about 3 minutes. Cool the oats in the pan for 2 to 3 minutes. Grind the toasted oats in a food processor until they reach the consistency of whole-wheat flour, about 3 minutes.
Heat a waffle iron according to manufacturer's directions.
Whisk together the toasted oat flour, all-purpose flour, sugar, baking powder, salt, and baking soda in a medium bowl. Whisk the eggs and melted butter together in another bowl, then add the buttermilk. Add the wet ingredients to the dry, and stir until combined. Rest the batter for 5 minutes.
Ladle the recommended amount of waffle batter into the hot iron. Close the iron top and cook until the waffle is golden on both sides and is easily removed from the iron. Repeat with remaining batter. Serve immediately or keep warm in a 200ºF oven until ready to serve.