Rosemary is a short point-and-click adventure centered around the theme of childhood memories. When Rosemary discovers a photograph of a forgotten friend, she cannot recall what has become of him, so she decides to travel back to the town of New Rye to find out if it brings back any memories. At the start of the game three locations are available that the girl can explore freely. To progress in the game and solve the mystery, Rosemary's memory needs to be pieced back together. By examining the environment she will recall certain events that are stored as photographs. Placing these correctly inside a diary completes lines of text, reveals additional information and changes the environment, sometimes introducing new object or other subtle changes.
The modern day New Rye is dark and deserted, but at any location Rosemary can travel back to the same place in her memory by clicking a button in the bottom left corner, revealing characters and events from her younger days. Retracing her steps opens up additional locations and a number of puzzles that also encompass collecting objects, storing them in an inventory and using them in the environment.
The main actions are shown through buttons at the bottom of the screen: look at, walk, talk, listen, smell, take, open/close, dig, hit and put. Hovering over locations in the environment with the mouse cursor reveals a tooltip with the name written in text, indicating that the player can interact with it.