In a skillet over medium heat, cook the ground beef, onions, and green pepper until no pink remains. Drain all but 1-2 Tablespoons of the fat from the pan.
In a slow cooker, combine the cooked beef and veggies and all the remaining ingredients, up to the rolls. Stir to combine. Set the crock pot to low and cook for 4-6 hours. It helps if you can give these a stir every hour or so to keep it from sticking, but it's not totally necessary.
To serve, pile the sloppy joe mixture onto the buns. Top with the cheese, pickles, and onions.