A roast set looks like an individual performance and is almost always a collective product. The format's demands make joke-by-joke writing by committee the only reliable way to fill it.
The format demands relentless density
A roast set is built of short, self-contained jokes with no narrative connecting them, which means the material is consumed at an unusually fast rate.
A stand-up hour can carry a weaker stretch on the strength of a story. A roast set exposes every line individually, with nothing to hide behind.
Producing that many strong lines about a small set of subjects is beyond what one writer reliably generates on a deadline. The failure rate on jokes is high even for excellent writers.
Volume raises the hit rate
Teams generate a very large pool of jokes about each subject, from which only the strongest survive. The selection is what produces the density.
Because the targets are known in advance, writers can work in parallel on the same subject and compare results directly.
Duplicate premises are common when several writers approach an obvious angle, and resolving those overlaps is part of the assembly work.
Material is tested before the taping
Performers run selected lines at clubs beforehand, which identifies which jokes work when the audience has no context and no affection for the target.
That test is imperfect, since a roast audience knows the subjects and reacts differently, but it removes lines that fail outright.
Ordering is then adjusted so the set opens strong and closes on the most reliable material, which is standard structure rather than anything specific to roasts.
Legal and editorial review is real
Jokes about identifiable people are reviewed before broadcast, and lines touching on matters that could be read as factual assertions are frequently cut.
The convention that roast material is understood as insult rather than claim does substantial work here, and the review exists to keep material clearly on that side.
Broadcast standards remove further lines, which is why the taping runs far longer than the version that airs. A recorded roast is routinely cut by a substantial fraction before broadcast.
Consent is what makes it function
Subjects agree to participate knowing the intent, and the closing response from the person roasted is a structural part of the form.
That agreement is what separates the format from ordinary insult, and it is why the same lines would be unusable in any other context.
The affection underneath is genuine and is the reason performers accept material about themselves they would never otherwise allow. Without it the evening would simply be cruelty performed in front of cameras.