Combine the rice flour, tapioca flour, teff grain, baking powder, baking soda, and salt in a large bowl and stir with a whisk.
Mash the banana with a fork or potato masher in a medium bowl. Add the soymilk, brown sugar, oil, ground flaxseed, molasses,and vanilla extract to the medium bowl and mix thoroughly.
Pour the liquid mixture into the flour mixture and stir until well blended, and any large clumps of rice flour are gone.
Let the waffle batter stand for 3 to 5 minutes while preheating a waffle maker according to the manufacturer's directions. This will allow the rice flour to absorb a bit more of the moisture.
Stir the batter a bit more if necessary to get rid of any remaining rice flour clumps.
Spray both grids of the waffle iron generously with oil. (See note.) Pour or ladle the batter onto the center of the iron, covering no more than two-thirds of the iron's surface for the first waffle. Adjust the amount as needed for subsequent waffles.
Bake each waffle for 3 to 5 minutes, or until it can be removed easily, spraying both grids generously with oil prior to each waffle.