Modify rolo to look for a file .rolo in each rolo user's home directory that contains the full pathname to that user's phone book file. For example:

$ cat $HOME/.rolo
/users/steve/misc/phonebook
$

This one's really easy, just a few lines of code need to be added. Here's how the beginning of the script should now read:
if [ -s $HOME/.rolo ] ; then
PHONEBOOK=$(cat $HOME/.rolo)
else
: ${PHONEBOOK:=$HOME/phonebook}
fi

export PHONEBOOK