At one point Polanski even rang Levin to inquire exactly which issue of a magazine one of the characters was reading when they noticed a shirt advert. Ira Levin replied that he just made this up.
Adult Fear: The real horror comes from not the supernatural themes - which are rather subdued by today's standards - but from Rosemary's predicament: she is manipulated and conspired against by everyone around her, and even when she realizes this and fights back, she is powerless to stop them.
The Bad Guy Wins: The cultists succeed in their plan to spawn the Antichrist — and it seems that they've drawn Rosemary herself into their ranks.
The novel subverts it a little. While Rosemary does agree to raise her baby, it's because she hopes that she can influence him to reject his destiny and embrace his human side. This is shown when she demands that the baby be named Andrew (instead of "Adrian", after the cult's founder) and not wear black all of the time.
Call Back: plenty, the film really makes use of horrible little moments or elements that come back later, for instance:
Dr. Shand: briefly mentioned before as another Castevet friend, introduced to Rosemary at New Year's, and showing up to drive them from Dr. Hill's.
The paintings in the Castevet's home: the spaces on their walls are noted by Rosemary when they first have dinner there. later a burning building and a sinister bearded man over looking the ritual are elements of Rosemary's "dream"; and later we see, in the final scene, the picture of the burning church in the hallway, and the painting of the man in the living room, which is actually a portrait of Adrian Marcato, Roman's father.
The very first scene: When Nicklas is showing miss Gardenia's apartment, there are plenty of herbs everywhere, which is confirmed that she grew things with Minnie. Then Nicklas notices the dresser in the hallway blocking the closet for some strange reason, revealed that the closet has a secret door between the apartment and the Castevets' next door. And before any of that: Rosemary noticing a strange note made (presumably) by Miss Gardenia ("...i can no longer associate myself") alluding to the Castevet's evil influence. And plenty more...
Wait a second... is that William Castle outside the phone booth?
That's Tony Curtis on the phone as the actor who's blinded and replaced by Guy in a play.
Clap Your Hands If You Believe: Inverted with Rosemary. She was raised Catholic but has drifted away from the church, and the Castevets find her a ripe target. Meanwhile, her stolidly Catholic sister can sense that Rosemary is in danger but Rosemary doesn't get anything of the sort.
Friends Rent Control: A struggling actor and his non-working wife living in a prewar apartment in an exclusive Upper West Side building that, even in the '60s, a hedge fund manager could barely afford in real life. Justified in that New York rent control prevents the landowner from raising rent above a certain percentage of what the previous tenant (an elderly woman who had been there for decades) was charged. The superintendent even comments on this, saying that they would charge a great deal more if they could.
The baby is suggested to have inherited them as well.
Hollywood Satanism: Subverted. The Satanic coven is probably the closest you'll ever come to actual Satanists in a Hollywood film. The only ritual we see doesn't feature big black robes or child sacrifice, but rather a bunch of old people singing naked.
Jerkass: From the beginning Guy was more than a bit of a jackass. Seriously, what man repeatedly states to his wife's face that he thinks her haircut makes her look hideous and that it's the worst decision she's ever made?
The night after Satan impregnates her, Rosemary notices some scratches on her. Guy tells her he got too excited last night and then handwaves it as "Baby Night." Outside of the fact that Guy is covering for the fact that he let Satan rape his wife, he covers by saying he basically raped her unconscious body, scratching her in the process, and thinks that's an acceptable cover story.To top it off, he says "it was kind of fun, in a necrophiliac way".
Nightmare Face: In the final scene when Rosemary discovers her baby. While not disfigured, the look on Rosemary's face when she first sees her child, and her eyes go INCREDIBLY WIDE...you don't even have to see what the baby looks like, her horrified expression tells it all.
Also Satan, though (thankfully) we don't see too much of it.
Sequel: A Made-for-TV Movie (Look What's Happened to Rosemary's Baby) was produced in 1976, while Ira Levin penned a sequel to the novel (Son of Rosemary) in 1997.
Shoot the Shaggy Dog: Rosemary becomes suspicious of her husband and the neighbors he's befriended. She discovers her suspicions are all too horribly true. She tries to escape. She fails. It wouldn't have made any difference if she'd succeeded. In the end, she just gives up. What was at stake? Everything.
She doesn't give up in the book, though. She first plans to grab the baby and jump out the window with it to kill it, then plans to agree to raise it, with the intent of guiding it to be a good person and not evil.
Shout-Out: Rosemary mentions in passing that she and Guy enjoyed watching a production of The Fantasticks the other day.
Significant Anagram: Steven Marcato the warlock. Roman Castevet the neighbor. They're one and the same.
Title Drop: In-universe example. Rosemary reads a book titled "All them witches". When she starts growing more and more paranoid she starts rambling "Witches... witches... all of them, witches... All them witches!" and then seems to laugh to herself.