Preheat oven to 425 F. Prepare pork first and make the sauce while it cooks.

Pork: Place pork on cutting board and season with sage, garlic, salt and pepper. Rub seasonings into meat. Set aside.

Lay prosciutto in two sections onto cutting board so slices overlap slightly. Each section should be large enough to cover a tenderloin. Place tenderloin on edge of prosciutto and roll up tightly. Repeat with other tenderloin.

Place on metal cookie sheet and drizzle with olive oil, turning to coat. Place in preheated oven and bake for 15 minutes, then turn pork over.

Add grapes and pearl onions to pan and toss around to coat with pan juices. Return pan to oven and continue to cook for 10-15 minutes until pork reaches internal temperature of 165 F. Remove from oven and let rest 5 minutes.

Sauce: Combine sauce ingredients in saucepan and simmer over medium heat until mixture is reduced to about 3/4 cup volume. Season to taste with salt and pepper. Add roasted grapes, onions and pan juices to the sauce.

To serve: Slice pork on the bias and serve drizzled with sauce.