Preheat oven to 400F. Allow fish filets to come to room temperature before roasting.
Combine mustard, maple syrup, salt, pepper and lemon juice in a small bowl. Set aside.
Rub room temperature fish with the olive oil and place on a pan on top of a sheet of parchment or wax paper. Place in preheated oven and cook 8 minutes. Remove from oven and glaze all sides of fish filets with a pastry brush, return to oven and roast an additional 8 minutes or until done to your liking.
Remove from oven and use pastry brush again to reglaze the fish with pan drippings. Serve with boiled or roasted new potatoes (skin off) and lemony green beans.