Pregnant Rosemary is expecting her first child, and along with the usual worries of bearing a child, she comes to suspect her neighbours and husband of being a witches' coven; at first she is paranoid that they want to use the blood and flesh of her first child in a ritual, but it is soon revealed that the child belongs to Satan. Naturally she is horrified at the ordeal, though towards the end her horror begins to wane as she rocks the child.
Despite being rated an 18, I didn't really find this film scary or obscene in any way; I suppose in the mid-sixties a theme of Satan worship would have been rather controversial and frightening for people (I assume), but today it seems rather dated, with far more disturbing films available. Perhaps the scariest part was when the camera briefly zooms in on a woman that committed suicide, showing blood. Despite this, I enjoyed it, as the character Rosemary Woodhouse had me constantly on the edge of my seat.
My favourite parts were how the music added suspense - I particularly liked the opening song/main theme music as it reminds me of the creepier Ennio Morricone songs with Edda Dell'Orso (my kind of music from the 60s and 70s) - and the slow build up to her hysteria.
However, I would have liked to have seen what Rosemary's Baby looked like, being half-Satan and all. The inverted cross hanging above the baby's crib was a nice touch for adding further creepiness, as well as the crowd yelling "hail Satan" and "God is dead" amidst Rosemary's cries of "oh God".
I also liked the constant imagery of medicinal/ritualistic herbs throughout, like the foul-smelling herbs in hers and the woman that committed suicide's necklace, which was claimed to bring good luck, the herb gardens that keep getting mentioned and promised by the husband, the medicinal drinks that her Satan-hailing neighbour makes her take, as well as Rosemary's own name. These herbal references hint at witchcraft from the beginning, perhaps foreshadowing what the family-to-be would get into by moving to the old deceased woman's apartment.