The meat is the whole abdomen of a radroach. Since radroaches appear less frequently in Fallout: New Vegas than in Fallout 3, radroach meat is more difficult to find. The effects of radroach meat in Fallout: New Vegas are notably different. It restores a small number of hit points, but gives a high dose of radiation, in addition to a -1 penalty to Strength.
It's bad, but at least its not Bloatfly meat.