Heat the oven to 425. Peel and chop the sweet potatoes and roast for 30 minutes, turning once, until fork tender.
Meanwhile, prep and dice/shred all the veggies, and wash the beans. Cook the rice and lentils if not already made.
Caramelize the onion: in a medium frying pan, cook the onion over medium heat for 20 minutes, until caramelized.
In a large bowl, place the drained beans, and mash well with a potato masher or fork. Then mash in the sweet potatoes. Stir in the lentils, rice, garlic, veggies, and all spices.
Form into patties. Pour a little olive oil on a large frying pan, and cook over medium heat for about 5 minutes each side, turning once.
Serve on buns with the caramelized onions and any toppings you enjoy.