Mix pork rub seasoning and Chinese five-spice powder together in a small bowl. Rub all over pork roast.

Place sweet potatoes into the bottom of a slow cooker; add brown sugar and butter. Place roast on top and season with salt and pepper.

Cook on Low until roast is fork-tender, 6 to 7 hours. An instant-read thermometer inserted into the center should read at least 145 degrees F (63 degrees C).

Cook's hints -
Do not add any water to the slow cooker.

If pork doesn't seem quite done after 7 hours, turn cooker on High for about 45 minutes longer.