Star Wars tells a single story in chronological order and the currently available versions of all movies are presented to directly support this narrative. This is Anakin’s story — the rise, fall and subsequent redemption of the boy who became Darth Vader.
Episode VII (and VIII and IX) should be watched last, with "Rogue One", "Solo" and subsequent anthologies seen either last of all or dropped in as palate cleansers at any point after "Return Of The Jedi". In this order, I put them after Episodes VII-IX to not break up the entirety of the story overarching every Episode, but they can certainly be watched after Episode VII.
While "Rogue One" is indeed a prequel to "A New Hope" (as the Han Solo movie is), there is little to recommend watching it beforehand as none of the callbacks or references would make sense. By the same token, the film’s dramatic impact is drastically reduced without a broader context or the weight of knowing what is to come.