Preheat oven to 400°F or 200°C.
Add potatoes, carrots, garlic and fresh/dried rosemary to a baking sheet or oven-safe dish. Drizzle with oil and season with salt and pepper to taste. Toss to coat.
Roast for 30-45 minutes or until fork tender and crisp.
Meanwhile, make the fish papillotes.
Cut parchment paper or foil into 12-inch squares and arrange them on a work surface. Fold each piece in half to form a crease down the middle.
Combine veggies for the fish with herbs, water, lemon zest and olive oil. Divide veggies over the squares. Arrange one fillet on top of each pile of vegetables, then season fillets with a squeeze of lime, salt and pepper.
Optional: top each fillet with an extra herb sprig.
Fold each square of paper or foil to form a sealed pouch. Transfer pouches to a baking sheet and bake in the oven until the fish is cooked through, about 20 minutes.
Serve with roasted potatoes.