Preheat the oven to 400°F
Slice the mushrooms, carrots, celery, and onion and transfer to a parchment lined baking sheet. Roast the vegetables for 20 minutes.
Add the roasted vegetables, seasonings, and drained black beans to the food processor. Make sure black beans are well drained to avoid adding too much moisture to the burger. Blend for 1-2 minutes, or until all the ingredients are incorporated and the mixture is mostly smooth with some texture. If the mixture has too much moisture (is not thick and does not hold shape when forming patties), add cooked quinoa or brown rice and blend for 1-2 minutes until smooth.
Once the black bean mixture is complete, begin forming patties. The mixture should make 6 to 8 patties.
Place the patties on a parchment-lined baking sheet and bake for 25 minutes, gently flipping halfway through.
Serve on your favorite bun with lettuce, tomato, and avocado. Enjoy!