Season the shrimp with salt, pepper, cumin, and oregano. Cover and refrigerate.
In a medium skillet, heat the oil over medium-high heat. Add the onion, garlic, and salt. Cook until softened, 8-10 minutes, then add the crab meat and green onion. Taste for salt and cook 5 minutes, then add the shrimp. Cook, stirring frequently, until shrimp are just cooked—5 minutes. Take off the heat and toss the seafood in about ½ cup of the sauce.
Preheat oven to 375 degrees.
Spread 1 cup of sauce down the center of a 7 1/2’’ x 10 1/2’’ baking dish (or a similar sized pan). Evenly divide about 1 ¼ cup of the cheese and the seafood filling into each tortilla, roll them up, and place them seam side down, centered in the pan. Pour the remaining sauce over and sprinkle with remaining cheese. Cover with foil and bake for 15 minutes. Remove the foil and bake 15 minutes more until cheese is melted and gooey.
Remove from the oven, garnish with cilantro and radish, and serve with pico de gallo, cotija cheese, cilantro, fresh lime juice, fresh acovado, black beans, or rice.