Step 1Heat the oven to 500 degrees. Tie kitchen string tightly around the roast at intervals of about 2 inches. Rub 1 tablespoon salt over the surface of the roast. Thread the herbs under the string along the roast, lengthwise, alternating the bay, thyme and the rosemary sprigs.
Step 2Place the roast in the center of a roasting pan that will accommodate the roast and shallots in a single layer. Toss the shallots with one-fourth teaspoon salt and the olive oil and arrange them around the roast.
Step 3Roast the pork until it begins to look crisp and the shallots just begin to color, 20 to 30 minutes. Baste with the pan juices, and stir in enough water to create a thin layer of liquid in the bottom of the pan, about one-fourth cup. Reduce the heat to 350 degrees and continue roasting (basting often and adding water as needed) 30 to 50 minutes longer, until the meat is nearly firm to the touch and still slightly pink at the center, or a thermometer inserted into the thickest part of the roast registers 140 degrees.
Step 4Remove the meat and shallots to a platter and tent with foil. Place the pan over medium-low heat, add the currants, one-half cup water, vinegar and sugar to the pan juices, and stir, scraping up any brown bits. Raise the heat to medium and cook until the sauce takes on flavor from the currants, 3 to 5 minutes. Season to taste with salt and pour sauce over the roast and shallots. Remove strings and herbs from the roast and slice to serve.