Roasted Oysters with Pickled Radishes, Carrots and Celery Root

Put the radishes, carrots and celery root in a medium bowl. In a small saucepan, combine the vinegar, water, the sugar and salt. Bring to a boil over high heat, stirring until the sugar and salt are dissolved. Pour the pickling liquid over the radishes, carrots and celery, and cover with a plate to keep them submerged. Let cool to room temperature.
Cover the bowl with plaster wrap and refrigerate for about an hour. Transfer the pickles and liquid to a container, cover and refrigerate.
In a medium skillet, heat the oil over medium-low-heat. Add the leek, shallot and garlic and cook until soft, about 7 minutes. Season with salt and pepper and set aside to cool. Meanwhile, make the brown butter. In a small skillet, cook the butter over medium heat, swirling the pan, until the better melts and the milk solids turn golden brown, about 3 minutes. Set aside to cool.
Preheat the oven to 450°F, or prepare an outdoor grill and let the coals burn until they turn white.
To keep the oysters from tipping, spread the rock salt in a large baking pan and nestle the oyster in the salt, being careful not to spill the juices. With a spoon, gently lift each oyster from the shell, slip about 1/4 teaspoon of the cooked leek mixture into the shell, and set the oyster on top. Drizzle with a little brown butter.
Bake in the over or cook on the grill until the oysters are just heated through, about 5 minutes. Top each oyster with a few pieces of pickled radishes, carrots, celery root and chives.