Preheat the oven to 375 degrees F (190 degrees C). Line a shallow roasting pan with aluminum foil.

Season pork loin with salt and pepper. Wrap bacon slices around pork loin and secure with toothpicks.

Heat a large skillet over medium-high heat. Cook pork loin in the hot skillet until golden brown on all sides, about 10 minutes. Transfer pork loin to the prepared roasting pan.

Stir together onion, honey, balsamic vinegar, red wine, and rosemary in a medium bowl until well combined; spread over pork loin.

Roast pork loin in the preheated oven for 15 minutes, then sprinkle with raisins. Continue cooking until an instant-read thermometer inserted into the center reaches 145 degrees F (63 degrees C), about 15 minutes more. Remove from the oven and allow to rest for 5 minutes before removing toothpicks and slicing.