Spray slow cooker with cooking spray. Add pork, fat-side (white-side) up. Add root beer, spices, and enough water to cover the roast.
Cook on high for 30-60 minutes, then cook on low for another 5-8 hours. Alternately, skip the high temp and just cook on low for 8-10 hours (that's what I usually do, as I'm running out the door to work as soon as I put the roast in).
Carefully remove pork (tends to fall apart and splash hot liquid). Let cool enough to touch, then separate meat from fat using two forks with help from your bare hands. (To be honest, I mostly use my bare hands if it's just me and my husband eating it.) Shred the pork with the forks and/or your clean hands. Discard fat and cooking liquid. Use immediately or freeze.
If using with BBQ sauce
Rinse out the slow cooker. Put pulled pork back in the pot and add 1/4 cup to 1/2 cup of water to ensure moistness. If you're using BBQ sauce, add it to the pork and mix to combine. Don't be stingy!
Cover slow cooker and cook on low for about an hour. Uncover and continue cooking for an additional 30-60 minutes to thicken as needed. Turn off slow cooker and allow to rest, covered, until it's time to eat.
Try not to take too many tastes of the pork or you won't end up with any left for dinner!