Arrange 12 slices of baguette on the broiler pan in a single layer. Toast bread lightly on each side under broiler. Remove broiler pan from broiler. Spread out sliced pears on cutting surface and squeeze the juice of a wedge of lemon over the slices to keep them from browning. Place a slice of pear on each toast and top with Roquefort crumbles and walnut pieces. Return pan to broiler 6 inches from heat source and broil toasts 2 or 3 minutes to melt cheese and toast walnuts. Transfer to a plate and start snacking!