Alchemy.Events.on_role_update

You're seeing just the macro on_role_update, go back to Alchemy.Events module for more information.
Link to this macro

on_role_update(func)

(macro)

Registers a handle triggering whenever a role gets updated in a guild.

args : Alchemy.Guild.role, Alchemy.Guild.role, snowflake

Receives the old role, the new role and the id of the guild that it belongs to. The old role may be nil if it was not already cached when the event was received.