In a large skillet heat 1 tablespoon of the oil, and then add the garlic and onions. Cook over medium heat, stirring, until the onion softens, about 5 minutes. Add the spinach and cook, stirring, just until the spinach is wilted, about 3 minutes. Transfer the mixture to a bowl and cool. When cool, stir in the all 3 cheese . Taste and add salt and pepper as desired.
Position a rack in the center of the oven and preheat the oven to 425F.
To prepare the tenderloin, use a sharp knife to make a lengthwise cut down the center of tenderloin, two-thirds of the way through the meat. Press the tenderloin open and, using a meat mallet, gently pound the tenderloin until it is flattened into an approximate rectangle about 1/3-inch thick.
Take the spinach mixture and spread it evenly over the cut sides of the pork, leaving a 1-inch border on all sides.
Starting with the long side of one of the rectangles, carefully roll up the pork jelly-roll style. Tie the pork at 1-inch intervals with kitchen twine.
Place the pork loin in a baking dish. Add 1 tbsp olive oil to the pork loin and rub it all over the season the pork on all sides with thyme, rosemary, salt and pepper. Pour white wine in bottom of pan.
Place the pork loin in the the oven and roast for about 25 minutes, or until the internal temperature of the meat reaches 145F to 150F at the thickest part.
Transfer to a cutting board and let them rest for about 15 minutes before cutting.