If you want a more elegant look, take the time to cut the ingredients to the same size, approximately 1-inch squares. For a more homestyle appearance, as shown in the pictures, some variability is fine as long as none of the pieces is extremely large or small. The exact sequence of how to skewer ingredients is up to you but I have provided a suggestion that worked well with the quantity of ingredients I had.
Separate the onion into layers and cut 36 pieces of onion about the same size as the pepper pieces
Thread the meat and vegetables onto 12 skewers in the following order: Pepper, Pancetta, Onion, Pork, Pepper, Pancetta, Onion, Sausage, Pepper, Pancetta, Onion, Pork.
On the bottom of a shallow roasting pan large enough to hold the skewers in a single layer, put the rosemary, sage, bay leaves, oregano, juniper berries and garlic.
Put the skewers on top. Season generously with salt and pepper. Drizzle with olive oil.
Roast at 400°F until the meat is cooked, approximately 20 to 30 minutes, basting occasionally with the oil from the pan.
Arrange the skewers on a serving platter. Pour the oil over top being sure to add the cooked herbs and garlic. Serve immediately.