Cook the millet, boil a sweet potato, and boil the eggplant. You could also cut it in quarters, oil it, and roast it on an oiled baking sheet for 30-45 minutes until its golden and soft.
Fry the chopped onions in an oiled skillet with the rosemary. Make sure they are browned well before you shut the heat off and cover it.
Peel the sweet potato and eggplant after they've cooled a bit, then add the finished millet to a mixing bowl and mush it all together with your hands. The eggplant and potato will be easy to turn into a mush.
Add the onions last, some salt and pepper, and fold that together a few times. Put it in the fridge to cool, that way it will be easier to roll the meatballs and less sticky.
When it's more or less cool after a half hour start rolling the meatballs. Dip them into the flour and flour your hands, get them evenly coated. Bake them on an oiled cookie sheet for 30-40 minutes until golden, turning them on each side every 10 minutes. You could also pan fry or deep fry them.