Season the pork roast with salt and pepper and sear on each side.
Slice the onions and apples and add them to the bottom of a 6 quart slow cooker. Place the pork roast on top of the apples and onions. Pour the root beer over it all and cook on low for 7-8 hours.
Remove the pork and shred. Discard the cooking liquids, apples and onions. Return the shredded pork to the crock pot and stir in one 18 ounce bottle barbecue sauce.
Serve on buns.
Notes
To freeze leftovers, place in a heavy duty freezer bag and press out all the extra air and seal. Will keep for 3-4 months.