1. In a large bowl, mix vinegar, oil, cumin, pepper, and garlic.
2. Rinse beef, turkey, and sausages, pat dry, and coat in vinegar mixture.
3. Lift out turkey, drain, and wrap each piece with prosciutto.
4. Thread 2 metal skewers (about 13 in. long) parallel and about 2 inches apart through the longest part of the beef. Thread 1 skewer lengthwise through each turkey tenderloin. Thread sausages lengthwise onto 2 or 3 skewers.
5. Lay skewered meats on a grill over a solid bed of hot coals or over high heat on a gas grill (you can hold your hand at grill level only 2 to 3 seconds); close lid on gas grill. Brush meats once or twice with remaining vinegar mixture and turn as needed to brown evenly. Cook beef medium-rare, about 20 minutes, or medium, about 25 minutes; cut to center of thickest part to test. Cook turkey and sausages until no longer pink in center of thickest part (cut to test), 13 to 20 minutes for turkey, 12 to 15 minutes for sausages.
6. Place skewered meats on a platter. To serve, slice beef and turkey from skewers. Cut sausages in chunks.