ΔE 16.5, loose: different enough that you should pick on purpose. Grave Robber is a little lighter, much more saturated than Rough Iron.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Grave Robber is a little lighter, much more saturated than Rough Iron.
The same difference applies the other way round: Rough Iron is a little darker, much more muted.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.
See Rough Iron on the colour wheel See Grave Robber on the colour wheel
All matches: Rough Iron equivalents · Grave Robber equivalents