How to Make It
In a small bowl, combine 1/4 cup of the oil with the thyme, garlic, cracked peppercorns, and juniper berries.
Set the bone-in roast on a rack in a large roasting pan; alternatively, set the boneless roasts on a rimmed baking sheet, leaving as much room between them as possible. Rub with the seasoning mixture, coating the roasts completely. Cover with plastic wrap and refrigerate overnight. Bring the meat to room temperature before proceeding.
Preheat the oven to 350°. Rub the meat with the remaining 2 tablespoons of oil and season with salt. Roast the venison in the center of the oven for 1 hour. Turn the roast, baste with the pan juices and roast for 1 hour longer. Turn the roast once more and cook for about 20 minutes longer for medium-rare, or until an instant-read thermometer inserted in the thickest part of the meat registers 125°. Let rest for 20 minutes before carving.
Preheat the oven to 500°. Rub the meat with the remaining 2 tablespoons of oil and season with salt. Roast the meat in the upper third of the oven for 25 to 30 minutes for medium rare or until an instant-read thermometer inserted in the thickest part of each roast registers 125°. Let rest for 10 minutes before carving.
To serve, untie the roasts. Stand the bone-in roast on a large carving board with the shank end facing up. Carve slices from the side, slicing the meat straight down to the bone; slicing against the grain produces a more tender piece of meat. Carve the boneless roasts into 1/4-thick slices. Serve at once with the Beach Plum Sauce.