Preheat oven to 400°. Toss the sweet potatoes in the olive oil & season with salt & pepper. Roast for 30 minutes until easily pierced with a fork.
Meanwhile, cook the quinoa. You may want to cook the whole package as directed on the box, then set the ½ cup aside for the patties.
Turn oven down to 375°.
Coarsely chop walnuts. Next, wilt the spinach with the salt & pepper, about a minute.
Grate the carrot with a microplane, grater, or food processor. You’ll want about ¼ cup for the patties.
Place the sweet potatoes into a food processor and pulse until smooth. Add in all remaining ingredients of the patties, except the cannellini beans. Pulse a few times until everything is mixed but not smooth. Add in the beans & pulse a few more times. The mixture should still have chunks of potatoes, be wet/sticky, but still easy to form patties. You can add more quinoa if it seems too wet to you.
Heat oil in a large skillet, then form the patties and place in the skillet. You’ll want enough room to cook the peppers in the same pan, following step 8. Cook 2-3 minutes on each side until cooked through and golden brown.