rolls.sh

#!/bin/bash

# Usage: rolls.sh PATH

for path in $1/**; do
  dirname=`basename "$path"`

  for file in $path/**; do
    exiftool -overwrite_original -headline="roll $dirname" "$file"
  done
done

❯ tree rolls
rolls
├── 001
│   └── Screen\ Shot\ 2017-04-12\ at\ 13.40.58.png
├── 002
│   └── Screen\ Shot\ 2017-04-12\ at\ 13.41.10.png
└── 003
    └── Screen\ Shot\ 2017-04-12\ at\ 13.41.17.png

3 directories, 3 files

Will write exif headline with roll 001 (image parent directory name)