Preheat oven to 200C. Cut the sweet potatoes in half, rub with a little olive oil and bake sweet potatoes for around 30 minutes or until soft. Remove from the oven, set aside and reduce oven heat to 180C. Meanwhile, cook the rice until fluffy and tender.
In a large mixing bowl, roughly mash the the beans, rice and sweet potatoes then add the finely chopped onions, garlic, oats and spices. Mix thoroughly to combine the mixture. If it feels too wet and sticky, add more rice or oats - it should be moist but moldable.
Roll the mixture into equally sized balls, then flatten slightly by gently pressing on each patty. Roll them in breadcrumbs (or sesame seeds) then place on a lightly greased baking sheet and bake for around 30-45 minutes, carefully flipping halfway in.