you can read a book.

These images were taken with a Pentax 645N with the 75 2.8 Lens. I developed them in Rodinal (1:100) for 60 minutes. It is very easy. I just mix 495 ml of water with 5 ml of Rodinal. I start with 10 inversions and 30 minutes later I inverted the tank 3 more times. Other than that I just read, watch a movie, fix dinner, whatever till the hour is up. Nothing can go wrong. Even the temperature is not that crucial. Some say that you can shoot the same roll of film at different ISO readings. I have not tried that yet. I used Kodak 400TX 120 film and shot it at 1600.

http://jbhildebrand.com/2011/tutorials/workflow-tutorial-2-stand-development-with-rodinal/