Further update / solution, in case there are others trying to convert a Freesurfer annotation to SUMA surfaces.
The issue arose because Freesurfer's annotation values are so massive (almost all are greater than 32767). I used 3dRank to lower the annotation values to something more reasonable, which gave me the expected 3dROIstats output.
Thanks to Pete Molfese for the suggestion!
EDIT:
for hh in "lh" "rh"
3dRank \
-prefix std.60.Schaefer2018_400Parcels_17Networks_ranked.${hh}.niml.dset \
-input std.60.${hh}.Schaefer2018_400Parcels_17Networks_order.${hh}.niml.dset
done
Edited 1 time(s). Last edit at 11/20/2019 11:41AM by dmoracze.