Master file_roots def:
# cat /etc/salt/master
file_roots:
  base:
    - /srv/salt/base
  dev:
    - /srv/salt/dev
  qa:
    - /srv/salt/qa
  prod:
    - /srv/salt/prod


Output from master:
# salt lana state.highstate -v
Executing job with jid 20150418160441932308
-------------------------------------------

lana:
----------
    State: - no
    Name:      states
    Function:  None
        Result:    False
        Comment:   No Top file or external nodes data matches found
        Changes:

Summary
------------
Succeeded: 0
Failed:    1
------------
Total:     1


top.sls
base:
  '*':
    - ntp


ntp.sls
openntpd:
  - pkg.installed


Debug output from minion:
[DEBUG   ] Fetching file from saltenv 'base', ** attempting ** 'salt://top.sls'
[DEBUG   ] Fetching file from saltenv 'base', ** attempting ** 'salt://top/init.sls'