Fold 4 large square pieces of parchment paper in half. Open, and lay on the half flat. Working on one side of the parchment paper, place each fish fillet and season with salt and pepper.
Scatter all the veggie/herb mix all around the fish.
Lift the parchment paper on 2 opposite sides to meet in the middle above fish. Tightly fold down the paper until it reaches fish, crimping to seal. Roll up and crimp the ends to seal really well. The steam shouldn’t escape during cooking.
Repeat with the remaining ingredients to make 4 packets.
Place the packets on a rimmed baking sheet and roast 15-20 minutes for thin fillets (like tilapia) or 20-30 max for thicker fillets (like cod).
Transfer packets to plates, carefully unwrap because the steam can be hot.
Serve with a drizzle of olive oil and freshly ground pepper.