Trim the pork roast of excess fat. It's okay to leave some on there-- just get rid of the large, visible slabs.
Place the pork roast on a work surface and sprinkle with the onion soup mix. Use clean hands to rub the mix into the meat, reaching underneath to reach all sides. Sprinkle generously with salt and pepper. Place the seasoned roast in your slow cooker insert.
In a medium bowl, whisk together the root beer and 1/2 cup barbecue sauce. Pour over the roast in the slow cooker.
Place thee lid on the slow cooker and cook on LOW heat for 10 to 11 hours, or until the internal temperature is above 190 degrees F. and meat is tender enough to pull away from the bone.
Remove the roast to a cutting board and let it sit to cool for just a few minutes. Pour out all but about 3/4 cup of the juices from the slow cooker. Use two forks to shred the pork, cutting around and discarding any fatty pieces. Place all of your pulled pork back into your slow cooker. Add about 1½ cups of barbecue sauce. Stir to combine and place the lid back on. Heat on HIGH for about 15 to 20 minutes, just until pork and juices are hot and bubbly. Use this time to heat up your buns and get the rest of your meal ready.
Scoop the pulled pork onto the buns and serve immediately.
Notes
Nutritional information is for pulled pork only (1 serving for 10 servings total). Buns should be counted as extra.
*If you don't wish to make such a large roast, you can use the same ingredients for a smaller roast too. You can likely cut down a bit on the cooking time, and use less barbecue sauce when adding it in at the end.
*For the most tender pulled pork, I do not recommend trying to short-cut the recipe by cooking it on HIGH heat. Low and slow is best!