The coach relative to the drive team is not assigned a role. S/he can do anything that doesn't involve touching the controls or the trident.
The role of the coach varies per drive team, but generally, the coach directs the drivers, supplies them with information, and coordinates between the members of the alliance. Stuff that should be expected of the coach (tuned to how autonomous the drivers want to be)
- Provide the time of the game clock at regular intervals (15 seconds), and a countdown for the last 15.
- Information on where other robots are and what they are doing.
- Information on situations where alliance partners need assistance, or are doing something the drive team needs to know of to adjust the robot for.
- Directions for specific situations (pin person x, get ball y, run over the bump)
- Quick communication with other alliance members for team efforts.
In short: The drivers have tunnel vision on their own robot. The coach eyes everything else and directs based on that.