Sprinkle roast with salt and pepper. Heat shortening in a skillet over medium-high heat. Brown roast on all sides; place in a slow cooker. Add undrained sauerkraut, apples and juice or water; blend. Gently add pierogies so they are partly submerged in the sauerkraut (as the roast cooks, more liquid will cover the pierogies). Cover and cook on low setting for 8 to 9 hours.