Roll and sausage is the other half of the Scottish morning order, the same floury roll as roll and bacon but with sausage in place of the rashers, and the sausage is almost always the square Lorne slab rather than a link. Lorne is a seasoned beef and pork mixture set in a loaf tin and sliced flat, so it has a fine, even texture and an edge that matches the roll exactly. That squareness is the working argument over a link: a slab lays flat and covers the whole face of the roll in one even band, where round sausages leave gaps and roll out of the bread as it is lifted. The roll is named first because in Scotland the roll is the fixed thing; the slab of sausage is what makes this roll and sausage rather than roll and bacon.
The craft is the griddle and the fat. The slab is cut to the width of the roll and cooked on a flat heat so both faces brown and the close-textured meat firms enough to hold its shape and not bend or slide when the roll is picked up. The fine grind cooks and renders fast, so the timing is to colour the surface without drying the centre to a board, and a link, where it is used instead, is split and laid open for the same reason, to get a flat browned face against the bread. The roll is a soft morning roll, dense enough to take the rendered fat without going to paste and soft enough to compress to the slab, filled and eaten the same morning because it stales quickly. Butter to the edges bridges the salt to the wheat; the sauce, brown or red, goes inside in a measured stripe so it cuts the fat without running through.
The variations are mostly what is added on top of the slab. A fried egg brings a yolk to manage against the flat sausage; a tattie scone makes it a fuller Scottish stack; black pudding adds a second savoury slab. Roll and bacon is the same roll with rashers instead, and the coarse Cumberland and sage-heavy Lincolnshire links are different seasonings on the sausage idea. Each deserves its own article rather than being crowded in here.