Remove the fell (tissue-like covering) from roast with a sharp knife. Insert blade of sharp knife horizontally through side of roast cutting a 1 1/2-inch wide slit through roast; remove blade. Repeat procedure 6 times, spacing slits evenly in roast. Lay half a slice of bacon on a narrow metal spatula allowing about 1 inch of bacon to extend over end of spatula. Slide spatula completely through slit in roast. Hold bacon securely, and remove spatula leaving bacon slice in roast. Repeat procedure with remaining slices of bacon. (A larding needle may be used to insert bacon in roast.)
Place roast, fat side up, in a shallow roasting pan. Brush roast with butter.
Combine 1/4 cup breadcrumbs, shallots, seasoned salt, salt, and pepper; sprinkle over roast. Insert meat thermometer, if desired.
Cover lamb lightly with well-buttered brown paper. Bake at 400° until desired degree of doneness: about 1 1/2 hours or 140° (rare); about 2 1/2 hours or 160° (medium); about 3 hours or 170° (well done).
Remove brown paper; sprinkle with remaining 1/4 cup breadcrumbs. Continue baking 10 minutes or until breadcrumbs are browned.
Transfer roast to a warm serving platter. Sprinkle with lemon juice. Let stand 10 minutes before slicing. Garnish with lemon slices, if desired.