Every year, after the nominations are announced, theaters do a series pass where you can watch all the nominated Best Picture films. This year, one of the films, Roma, which is currently on Netflix, won't be played in the usual Best Picture showcases because it was never originally licensed to most theaters. Roma had a small theatrical run (in order to qualify for the Oscars); during its peak it played at a handful of theaters in the major markets. Apparently Netflix offered the theaters the license around mid-December, after it had been released on Netflix, but they said no because they don't play movies that are VOD (or in this case, movies that are on Netflix).
AMC and Regal confirmed they won't be playing Roma. Cinemark has yet to confirm, but it's believed they won't either. The 7 other Best Picture nominees will be played (Black Panther, BlacKkKlansman, Bohemian Rhapsody, The Favourite, Green Book, A Star Is Born and Vice).