Is it necessary to restart IIS in order to ensure that changes to azman.xml are picked up, or will IIS figure out that the permissions in azman.xml have been changed?
You don't say how you're using AzMan. Are you using it as a Role Management Provider? At any rate, you (almost) never have to fully restart IIS; just recycle the app pool.
But to answer your question (assuming you did mean Authorization Store Role Provider), IIS (actually, the provider) should check for changes according to your setting for the CacheRefreshInterval property. The default is 60 minutes.