Roast fish in preheated oven until an instant-read thermometer registers 90°F when inserted in thickest part of fish, about 25 minutes. Remove from oven, and discard foil. Squeeze juice from reserved orange half over fish. Return fish to oven; roast, uncovered, until fish flakes easily with a fork and a thermometer inserted in thickest part of fish registers 125°F, 8 to 12 minutes. (Timing will vary depending on thickness of fish; for thinner fillets, begin checking fish after about 12 minutes when covered and after about 5 minutes once uncovered.) Remove fish from oven; let rest 10 minutes.