I am creating a simple ambient/explorer platformer. Because I want the player to only be able to see a new area once they have reached it, I decided to split up the world in rooms. However, I also want to implement a slight parallax-effect.
These effects always manage to look awesome.
How do I create a smooth camera movement for this?
The code you posted up there probably produces a kind of "snappy" camera movement as the player is walking around.
Keep track of where your camera is and where it needs to be next, and update it every frame by a tiny amount. This will create the smooth effect.
For these types of effects, I usually write a Camera Animator class.