I think a runner's role outfield is pretty much fixed but the
definition of a job scope of a runner in camp is very much more
diversified.
Back in camp, my runner helps with AOPs, telting maps, copying
maps, doing up presentation charts, typing stuff, collating
results, collecting money and so on. He helps in falling in the
platoon and when my commanders are unavailable, he marches my
platoon to the cookhouse.
I've seen some people abuse their runners even outfield. I know of
a CO who made his runner go back to base to collect food and cook
for him. Even ate his runner's food. Honestly most of the time the
people abusing runners are the specs, not much of the officers.
Some specs see the runner as a dangerous position due to his
proximity to the PC. Outfield when I'm down, my chain of command
goes PC --> Runner --> PS until the PS is properly briefed by
my runner then will the PS take over cos my runner practically
knows the whole situation and plan all the time.