Python script to e-mail an on call roster

I have a report that i am creating and distributing using the function on a button press, but with our ever changing group of workers I am constantly updating the e-mail addresses. Is there a function to use an on-call roster since that can be changed with a few clicks?

From the manual

rosters = system.alarm.getRosters()

for key, values in rosters.iteritems():

    # key is the roster name, values is a dict of usernames

    print 'Roster', key, 'contains these users:'

    for value in values:

        print '  ', value

So that gets me all of the rosters and the names of the people in them. But how can I use that to create an e-mail list from a individual roster to use

No user source tpye was specified, but this assumes the users are in an internal user source.

rosterUsers = rosters['rosterName']

userInfo = system.user.getUsers('default')

contacts =  [user.contactInfo for user in userInfo if user.get('username') in rosterUsers]

print contacts