Mr. Poitier often found himself in limiting, saintly roles that nevertheless represented an important advance on the demeaning parts offered by Hollywood in the past. In “No Way Out” (1950), his first substantial film role, he played a doctor persecuted by a racist patient, and in “Cry, the Beloved Country” (1952), based on the Alan Paton novel about racism in South Africa, he appeared as a young priest.