Place whole bell peppers on the grill. Cook, turning occasionally until evenly charred. Place into a plastic bag and allow to cool. Place sausages on the grill. Brown on all sides, then move over to indirect heat and allow them to cook through, about 10 minutes.
Heat black beans in a small saucepan over medium heat until heated through. Remove from heat and drain off liquid. When peppers are cool enough to touch, peel off skin, remove seeds and stem, and chop. Transfer peppers and beans to a medium bowl, and stir in salsa. Set aside.
When sausages are done, slice into 1/2 inch rounds, and stir into the pepper mixture. Place tortillas on the grill to warm, about 20 seconds. Spoon the sausage filling onto each tortilla, and sprinkle lettuce on top. Layer with sour cream and guacamole as desired.