How do I turn off Routine notifications?

You can now disable Routine notifications in the Android app by clicking on each Routine, and  then clicking the settings ('gear') icon for that Routine.

Under that Routine Settings page, see the "Notifications" option and toggle the switch to "Notifications Off" to disable them for that Routine.  You can turn notifications off for all Routines you want to mute and turn them back on anytime.