1To cut pork roast so that it can be filled and rolled, cut horizontally down length of pork about 1/2 inch from top of pork to within 3/4 inch of opposite side; open flat. Turn pork so you can cut other side. Repeat with other side of pork, cutting from the inside edge to the outer edge; open flat. If pork is thicker than 3/4 inch, cover pork with plastic wrap and pound until about 3/4-inch thickness. Remove plastic wrap.
2Heat 1 tablespoon of the oil in 12-inch nonstick skillet over medium-high heat. Cook garlic and mushrooms in oil, stirring frequently, until liquid has evaporated. Stir in spinach, bread crumbs and cheese.
3Spread mushroom mixture on inside surfaces of pork. Roll up pork; tie with kitchen twine. Heat remaining 1 tablespoon oil in 12-inch nonstick skillet over medium-high heat. Cook pork in oil until brown on all sides. Place pork in 3 1/2- to 4-quart slow cooker. Sprinkle with salt.
4Cover and cook on low heat setting 6 to 7 hours or until pork is tender.