We have used the dude to mass upgrade RouterOS software.

Is there a way to use it to mass update the firmware and trigger a reboot?

really,
With the recent security holes mikrotik should implement a native way to do a massive update
this would even help the brand promote itself and avoid forum threads because of outdated software,
as many do not upgrade as it is impossible to update hundreds of CPEs manually

upgrade via ROS AP connected all ROS clients will be nice option.