Mrs. Rogers was being hired as a maid.
Ethel and her husband killed their former employer to inherit the money of the elderly women.
She cooks and cleans for the guests on the island.
After the accusations, Mrs. Rogers faints and is given a glass of brandy when she wakes up. Unbeknownst to anyone, however, Justice Wargrave has slipped a lethal amount of chloral hydrate (a sleeping drug) into the brandy, and Mrs. Rogers dies in her sleep that night.