Working at Universidade Federal de Santa Catarina, in Brazil, there was a need to compare the permissions of all roles, side by side, to assist the coordinator to give capabilities and avoid inconsistencies in roles hierarchy.
So, i have made a admin report, that let the user choose which papers to compare, and prints a table, with lines being the capabilities, the coluns being the roles and we have used colors to determine the permission: white is not set, green is allow, yellow is prevent, and red is prohibit.

Hope you like, i am attaching an screenshot and a tar.gz with the code (that must be discompacted in moodle/admin/reports/ , and the file report_rolescapabilities.php moved to moodle/lang/en_utf8 ).