In a large bowl mix the corn, tomatoes, black beans, and cilantro. Cut the lime in half and squeeze the lime juice onto the corn salsa and mix. The olive oil can be added for additional flavor.
To make the Roast:
Place the roast in a 5-6 quart slow cooker, then top it with the ingredients evenly. Cover and cook on low for 8-10 hours or until tender. It should shred easily. Once it is done, shred the roast and serve over the potatoes with your choice of toppings and the corn salsa.