Step 1Remove the thin membrane surrounding the monkfish with a sharp knife. Set the fish aside.
Step 2Cook the yellow and green squash in rapidly boiling salted water until tender, about 5 minutes. Cool in a bowl of ice water. Drain and set aside. Repeat this process with each of the remaining vegetables (the carrots will take 4 to 5 minutes, the asparagus and haricots verts 2 minutes).
Step 3Heat the oven to 400 degrees.
Step 4Heat an ovenproof skillet over medium-high heat and add the oil. Season the fish with salt and pepper. When the oil is hot, sear the fish on all sides, about 3 minutes a side. Place the skillet in the oven and bake until the fish flakes with a fork and is cooked through, 15 to 20 minutes.
Step 5Remove the fish from the skillet, reserving the juices. To make the sauce, add the pancetta and Sherry vinegar to the skillet, and cook over medium heat until the liquid is reduced by half, about 2 minutes. Add the chicken stock.
Step 6In a separate pan, reheat the remaining vegetables. Add the parsley, thyme and marjoram and salt and pepper to taste.
Step 7Present the roasted monkfish in a nice cooking pan or on a platter, garnished with the vegetables and the sauce. To serve, carve the fish along each side of the bone running down the middle.