Heat oven to 450° F with the racks in the upper and lower thirds.
Place the bread crumbs on a rimmed plate or baking dish. Combine the mustard, paprika, and cayenne in a medium bowl. Season the pork with ½ teaspoon salt. Spread both sides of the pork with the mustard coating, dividing evenly, then coat with the bread crumbs, pressing gently to help them adhere.
Roast the pork on a large rimmed baking sheet on the top rack until an instant-read thermometer inserted into the thickest part (avoiding the bone) registers 145° F, 15 to 20 minutes.
Meanwhile, toss the broccoli rabe, oil, and ¼ teaspoon each salt and black pepper on a separate rimmed baking sheet. Roast on the bottom rack, tossing occasionally, until crisp-tender, 4 to 5 minutes. Toss with the cannellini beans.
Serve the pork over the broccoli rabe and beans with the lemon wedges, for squeezing.