1. Preheat oven to 400 degrees F. Line large sheet pan with parchment paper.
2. In a mixing bowl, toss together zucchini, sweet potato, and sweet corn, drizzle with 1 to 2 tablespoons olive oil, and sprinkle with salt.
3. Spread vegetables onto prepared sheet pan and roast in the oven for 10 minutes. Toss veggies to make sure they cook evenly and return to the oven for 10 minutes more. Check again and remove from oven when edges are starting to turn golden brown. If you have too many veggies for one sheet pan, you can do them in batches.
4. Place roasted veggies back into mixing bowl and mix in fresh cilantro. Cover and set aside.
5. In a small to medium saucepan, heat up black beans with a tablespoon of olive oil. When black beans are soft, mash with a fork or potato masher. Add a little water if needed. Season with a little sea salt if needed.
6. Heat a cast iron skillet (or nonstick skillet) over medium heat for about a minute. Add a few drops olive oil and place tortilla on hot skillet. Using a pancake spatula, flip tortilla every 10-15 seconds to heat up evenly on both sides. Remove to a plate or a tortilla warmer and make sure to cover with a clean towel or pot lid. Repeat with as many tortillas as you need for your meal, about 2 per person. Tortillas can also be kept warm in a 200 degree oven by placing in an ovenproof dish (like a pie plate) and keep covered with foil.
7. At the table, pass around the tortillas and each person can fill their tacos with roasted veggies and avocado. Garnish with a squeeze of lime.

Variations

1. Substitute some other vegetables, such as sweet corn, winter squash, red onion, or yellow squash.
2. Add some fresh baby arugula or some finely shredded green cabbage on the top of each taco.
3. Use pinto beans instead of black beans.
4. Serve with cassava tortillas (Siete brand) if you prefer them to corn tortillas.