Is it possible to use a gopro (specifically the hero 4 session) as a camera through the dashboard. Does it support video through usb into the roborio?
I don’t know but make sure you change the streaming quality, otherwise you will have the bandwidth of a twine bracelet.
Could be wrong, but I believe you’d then have to power it only with the robot which may make that difficult.
You’re wrong. 
The GoPro’s battery is allowed to be used since it’s integral to the device.