A roast was any cut of meat roasted.
In 2152, Malcolm Reed became pinned to Enterprise NX-01's hull. Fearing that he'd be blown up by the Romulan mine, he asked Jonathan Archer not to sever the spikes that held him there. He added that if he let Archer amputate his leg, Chef would serve "roast Reed" for Sunday dinner. (ENT: "Minefield")
In 2365, William T. Riker described the phaser beam from a Borg cube as "carving us up like a roast." (TNG: "Q Who")