In a spice grinder, combine the peppercorns, rosemary, sugar, mustard seeds, allspice and pepper flakes. Pulse until coarsely ground. Mix in a small bowl with the sea salt and garlic powder.
Coat the entire roast with the spice rub. Set on a baking rack over a rimmed baking sheet. Refrigerate uncovered overnight.
Light the Barrel House Cooker according to instructions. Just before adding the meat, add a chunk of cherry or hickory wood.
Place the grill grate in the lower third of the cooker. Add an aluminum pie tin onto the grate to catch the juices.
From the top of the roast, pierce the rod of the EZ-Load Turkey Hanger through the center of the roast. Screw the two cross bars onto the second to last threads, making an X to hold the roast. Hang the roast onto the H-Frame, and load it into the cooker.
Insert a temperature probe into the center of the roast, being careful not to touch the metal hanger.
Close the lid and smoke to an internal temperature of 100°F, about 2-2½ hours.
Open the bottom vent all the way and crack the lid. The goal is to raise the heat to create a crust. If the cooker gets above 425°F, just close the lid back to normal. Continue smoking until the meat temperature reaches 135°F, about 30-45 minutes.
Remove from the cooker. Tent with foil and rest for 30-45 minutes before slicing.