Remove thawed roast from package. Place in the crock pot and add salt and pepper.
Add 1-2 c. water, depending on the size of your crockpot. The water should be about 1/2 inch deep so the roast can stay moist.
Combine barbecue sauce, orange marmalade, and onion powder in a small bowl. Pour over roast. Cover crock pot with the lid and cook on low for 7-8 hours on low, or until beef is tender.
Carefully remove the roast from the crockpot and into a large bowl. Use two forks to shred it. Place beef back in the crock pot and add remaining 1/2 c. barbecue sauce; stir and heat for 15-20 more minutes, or until heated through.
Place beef on hamburger buns and top with pickle slices. Serve and enjoy!