IMDB lists most of the crew appearing in the first episode of season five, including Nairobi who was killed in season four. The main component of "Money Heist" is it's non-linear story, going from the current time of the heist, to when they were planning it. Hence, it's likely that Flores may appear in flashback scenes similar to Pedro Alonso (Berlin), Paco Tous (Moscow), and Roberto Garcia (Oslo) who all appeared in the series even after their characters' deaths.
The remaining members of the crew are all returning including favorites such as Tokyo (Úrsula Corberó), Rio, Denver (Jaime Lorente), Stockholm (Esther Acebo), Helsinki (Darko Peric), Raquel Murillo, and Rodrigo De la Serna's Palermo.
As shown by the teaser, Sierra and The Professor will also be returning seemingly as antagonists. In addition, Miguel Ángel Silvestre from "Sense8" and Patrick Criado from "La Gran Familia Española" are both set to join the cast for Season 5, according to Deadline.