In real life, Rose would have remarried within a few years of her husband's death.
She loved Charlie. She loved being married. She's a comfortable woman who attracts with little effort the kind of men who also want to get married again (the anti-Monks). She corresponds quite well to Christie's description in The Body in the Library of Addie Jefferson:
"She's the kind of woman," said Miss Marple, "that everyone likes. The kind of woman that could go on getting married again and again. I don't mean a man's woman--that's quite different."
Consequently, unlike with Blanche and Dorothy, Rose's continual singlehood is not entirely realistic. Sitcoms falter on this edge: the same people in the same location go through stuff and joke about it. Nobody moves on or marries. Nobody gets their own place. Permanent lock-down. And it's not entirely believable.
Intelligently, the writers eventually give Rose an ongoing, steady boyfriend, Miles, played by the excellent Harold Gould.
Harold Gould shows up early in Season 1 as a different character, Arnie, with a similar personality and back-story to the later Miles (aside from the surreal witness protection plot). It's a great example of the needs of chemistry--the actors work well together--outweighing the issue of continuity. He was the right guy to bring back as the "steady."
