The Curious Dreamer’s Dream Dictionary
by Nancy WagamanA moving or rolling boulder might represent momentum, critical mass, overwhelm, or the idea of being out of control.
Consider also the context of the boulder and how you felt about it.
See Stone, Hard Object, Big, Blockage or Obstacle
New American Dream Dictionary
by Joan Seaman - Tom Philbin2. Obstacles.
3. Severe, seemingly insurmountable difficulties are in the offing.