The Pork Blade Shoulder, aka Boston Butt is ideal for BBQ'ed Pork Sandwiches. However, that is a step or two beyond 'pot roast'.
Season the roast with salt, pepper and garlic (or your favorite BBQ rub), place it into the crock pot with some apple juice and water. Add a drop or two of Liquid Smoke, if desired. Cook it all day until it is fork tender and literally falling apart. Shred the pork and add some of the juices from the crock pot to keep it moist. You can now add some bbq sauce and mix it in or just make a sandwich (cheap old burger buns are best) and add the sauce on top.
An alternative is to place the pork roast into a baking dish with the apple juice and water, cover with foil and bake at 250° for about 5 hours, or until the internal temp of the meat reaches 195-200°. Follow the above for making "Pulled Pork".
You can use any other liquid, other than apple juice. Beer for example, but I think the apple juice is the most diverse without adding it's own flavor.
Of course the traditional way of making "Pulled Pork" is to slowly smoke it for about 10 hours in the grill.