In a 4-6 quart slow cooker, pour two cans of black beans with their liquid. Add the chopped onion, chili, paprika, cumin, oregano, and salt. Stir to combine. Place the shoulder roast on top. Pour over favorite salsa and top with the lid.
Cook on low 6-8 hours or high 4-5 hours. The meat is done when a fork is easily inserted in the meat and it shreds easily.
Remove meat from the cooker. If there is a bone in the roast, it should pull right out. Shred using two forks.
Return the meat to the cooker and stir together with the beans and cooking liquid.
Serve on corn or flour tortillas with desired condiments.