Preheat the oven to 250F (121C).
In a small bowl, add the brown sugar, paprika, red pepper flakes, onion powder, liquid smoke, salt, and pepper. Mix until combined.
Rub the pork shoulder butt roast with the spice mixture, ensuring you fully coat all sides of the meat.
Prepare a large pan with a roasting rack. Place the pork fat side up on the rack. Place in the oven and roast, uncovered, until the internal temperature of the pork is 190-195F (88-91C). Depending on the size of your pork shoulder butt roast, this could take anywhere from 4-10 hours.
Once the temperature has been reached, remove the pork from the oven and let rest for 20 minutes before cutting. If you would like to shred the pork, you can optionally wrap the pork in aluminum foil and let sit for around 45 minutes to soften the interior a bit.
Once the pork is done resting, cut or shred and enjoy!