A little bit of fish sauce adds a savory flavor to the sauce.
Arrange racks in the middle and lower thirds of the oven; preheat to 450°.
Grate 1 tsp. of zest from 1 orange. Cut the orange in half. Squeeze 1 half to yield 2 tbsp. of juice. Cut the remaining orange into very thin slices.
Season the fish with salt and arrange in a baking dish. Top the fish with the orange slices. Drizzle with 2 tbsp. oil.
On a large rimmed baking sheet, toss the asparagus with 1 1/2 tbsp. oil; season with salt. Arrange in a single layer on the baking sheet.
Place the fish on the middle rack of the oven and the asparagus on the lower rack. Roast until the fish is just opaque in the center and the asparagus is tender, 10 to 15 minutes (depending on the thickness of the fish).
Meanwhile, on a cutting board, chop the garlic with the orange zest, crushed red pepper, and 1/8 tsp. salt; mash with the flat side of a chef’s knife to form a paste. Transfer to a bowl. Whisk in the orange juice, fish sauce, and the remaining 6 tbsp. oil; stir in the parsley for the salsa verde.
Divide the fish and asparagus among plates. Top with the olives and salsa verde.