When the Death Star fires offshore of the Scarif base, Jyn and Cassian embrace, knowing there's no escape and they will die soon. I thought that scene was reminiscent of some much earlier (non-Star Wars) film with a couple on a beach while an H-bomb went off, however I can't remember. Is this a reference to another movie? If so, which?
You may be thinking of From Here to Eternity (1953). In a memorable scene, Burt Lancaster is lying on a beach when he is suddenly paralyzed. Jyn Erso comes to his aide but she, too, is paralyzed. They embrace in a kiss as the tide comes in and ultimately spell utter doom. (Much like Deep Impact, mentioned above). Since they are paralyzed, they can't hike the Appalachian Trail, and thus our hero and his heroin go to waste.
At least, that's what I get from this movie still.
You may be thinking of Deep Impact (1998). A meteor is heading toward Earth and impacts in the Atlantic Ocean. A woman and her father, who are on bad terms, make their peace and embrace on the beach as the massive tsunami draws the water up and slams into them (and the entire U.S. east coast) with massive force. The water makes it to the Appalachian Mountains, with some people barely escaping the rising water.
I made the same connection when I saw the end of Rogue One.
I am reminded of a dream sequence in Watchmen where Night Owl and the Silk Spectre share a kiss before being obliterated by the detonation of a nuclear bomb.
See if the following clip matches:
You may be thinking of True Lies (1994). In one scene, the lead character and his wife (played by Arnold Schwarzenegger & Jamie Lee Curtis, respectively) have been evacuated from the Florida Keys, where a terrorist organization has set a nuclear bomb to detonate. At a safe distance from Ground Zero, they kiss as the bomb detonates.
The scene is visually similar to the end of Rogue One; the main difference is that the embracing characters are not killed, and this scene does not mark the end of the film.