Preheat oven to 425° F. Roughly chop mushrooms and toss in olive oil. Spread in an even layer on a sheet pan and roast in the oven for about 20 minutes, until soft. Drain off excess liquid.
Place mushrooms in food processor and process until it reaches the consistency of ground beef.
Place ground beef and mushroom mixture into a large bowl. Mix with a spatula until well combined.
Place a large skillet over medium heat. Add beef mixture and cook until browned, using a spoon to break into small pieces. Add cumin, chili powder, paprika, garlic powder, black pepper, oregano, and tomato sauce. Mix well and bring to a simmer.
Spoon mixture onto tortillas, and serve with desired toppings.
