Preheat oven to 400 degrees. Place cod in a baking dish; rub with 1 tablespoon oil. Roast fish in oven until cooked through, 15 to 20 minutes. Let cool completely, then pat dry with paper towels. Flake with a fork.
In a large bowl, combine cod, egg, scallions, mayonnaise, lemon juice, mustard, breadcrumbs, parsley, hot sauce, 1/8 teaspoon salt, and 1/8 teaspoon pepper. Mix gently until ingredients just hold together.
Form mixture into eight equal-size patties. Freeze on baking sheets until firm, then wrap each in plastic and store in resealable freezer bags, up to 1 month. Thaw before cooking.
To serve the cakes: Heat 1 tablespoon oil in a large nonstick skillet over medium heat. Cook cakes until golden brown, about 2 minutes on each side. Serve hot.
Flash-freeze the fish cakes on a sheet pan 5 to 10 minutes so they'll hold their shape. Then wrap each in plastic.