The Sandwich Roquefort is built around the one French blue made from sheep's milk, and that single fact is what sets it apart from every cow's-milk blue it gets shelved beside. Roquefort comes from the Aveyron, ripened in the limestone fleurines of the Combalou cliffs where the Penicillium roqueforti veins run blue-green through it. Sheep's milk gives it a richness and a lanolin roundness no cow's-milk blue carries, under a salt and a piquancy that are pointed rather than soft. The build is a length of baguette, a thin spread of beurre demi-sel or none, and the Roquefort crumbled or pressed into the crumb, with little else so the cheese is the sandwich.
The logic follows from the milk as much as the mould. Because the fat is sheep's-milk fat, the cheese reads creamier and more savory than a cow's-milk blue at the same age, which changes what the bread has to do: it needs real body to absorb the salt and carry the richness, so a firm-crusted baguette works where anything soft goes slack. The piquancy is forward enough that the build stays lean and the counterweights stay sweet or crisp rather than savory, the standard moves being a few walnut halves for bitter crunch or a thin film of honey or fig against the salt. None of these are required; the cheese, the bread, and a little butter are a complete sandwich, and the additions widen it rather than fix it. It eats best at room temperature, where the sheep's-milk fat softens and the veins read fully; chilled hard, the cheese turns firm and the roundness that distinguishes it is muted.
For the readings that organize the sandwich entirely around managing the cheese, or that mash it with butter into a single spreadable paste, the catalog treats those as their own pieces: see Sandwich au Roquefort for the cheese-dominant build and Sandwich au Roquefort for the fork-and-butter paste. This entry stays on the cheese itself. Variations move along the blue-cheese rack: a cow's-milk Fourme d'Ambert is the gentler, rounder substitute for anyone who finds Roquefort too pointed, and stepping to a sharper, older Roquefort pushes the other way. The Sandwich Roquefort belongs with the cheese sandwiches the catalog groups under Baguette Fromage, the tradition that gives every regional French cheese its own treatment. Its specific contribution is the sheep's-milk distinction, a blue whose richness and roundness come from the animal as much as the cave, and whose name on the sandwich means that specific milk and no other.