Preheat the oven to 400°F (200°C). Line a baking sheet with parchment paper.
In a frying pan, heat the olive oil over medium heat. Add the diced onion and bell pepper, and sauté until soft, about 5 minutes.
Add the minced garlic, ground cumin, chili powder, salt, and pepper. Continue to cook for about 1 minute until fragrant.
Stir in the black beans and corn, mixing well. Remove from heat and let the filling cool slightly.
Take a corn tortilla and spoon about 2 tablespoons of the filling onto the center. Roll the tortilla tightly to form a taquito. Repeat with the remaining tortillas and filling.
Place the rolled taquitos seam-side down on the prepared baking sheet. Lightly spray or brush the tops with oil to help them crisp up.
Bake in the preheated oven for 15-20 minutes, or until golden brown and crispy.
Remove from the oven and let cool slightly before serving. Garnish with fresh cilantro and serve with vegan sour cream or guacamole if desired.