Preheat the oven to 425F and line two baking trays with parchment paper.

Drain the black beans thoroughly to remove as much excess water as possible. Spread the beans out on one of the baking trays in a single layer.

Add the sweet potatoes to one side of the second baking tray, and the onions, bell pepper, and garlic to the other side. Drizzle with oil and a pinch of salt, and toss to coat. Spread out the vegetables in a single layer.

Place both trays in the oven. Bake the black beans for 15 minutes on the top rack, and bake the vegetables on the bottom rack for 15-20 minutes, or until the potatoes are easy to pierce with a fork. Once out of the oven, allow to cool for 10 minutes.

Transfer the beans and baked vegetables to a food processor along with the oats, paprika, coriander, fennel seeds, crumbled bouillon cube, and tamari. Pulse until well combined and the mixture holds together, scraping the sides down as needed.

Scoop out 1/3 cup of the mixture at a time and shape into round patties, about 1/2 inch thick. Place the patties on a lined baking tray and spray both sides lightly with oil. Bake in the oven for 15 minutes.

While the patties bake, whisk together the oil, lime juice, agave, and a pinch of salt in a bowl. With a pastry brush, brush the tops of the patties with the lime drench, flip, and repeat on the other side. Return to the oven for an additional 5-10 minutes, or until golden brown on both sides.

Allow the patties to cool and firm up for 10 minutes. Brush with more of the lime drench before serving if desired.