diff --git a/ldapcherry/exceptions.py b/ldapcherry/exceptions.py
index bc8517d..44fb287 100644
--- a/ldapcherry/exceptions.py
+++ b/ldapcherry/exceptions.py
@@ -12,8 +12,11 @@ class MissingParameter(Exception):
         self.log = "missing parameter <%(key)s> in section <%(section)s>" % { 'key' : key, 'section' : section }
 
 class MissingKey(Exception):
-    def __init__(self, key):
+    def __init__(self, key, section, ymlfile):
         self.key = key
+        self.section = section
+        self.ymlfile = ymlfile
+        self.log = "missing key <%(key)s> in section <%(section)s> inside file <%(ymlfile)s>" % {'key': key, 'section': section, 'ymlfile': ymlfile } 
 
 class DumplicateRoleKey(Exception):
     def __init__(self, role):
diff --git a/ldapcherry/roles.py b/ldapcherry/roles.py
index 358316c..9479a78 100644
--- a/ldapcherry/roles.py
+++ b/ldapcherry/roles.py
@@ -8,6 +8,7 @@
 import os
 import sys
 
+from sets import Set
 from ldapcherry.pyyamlwrapper import loadNoDump
 from ldapcherry.pyyamlwrapper import DumplicatedKey
 from ldapcherry.exceptions import DumplicateRoleKey, MissingKey, DumplicateRoleContent, MissingRolesFile
@@ -16,6 +17,8 @@ from ldapcherry.exceptions import DumplicateRoleKey, MissingKey, DumplicateRoleC
 class Roles:
 
     def __init__(self, role_file):
+        self.role_file = role_file
+        self.backends = Set([])
         try:
             stream = open(role_file, 'r')
         except:
@@ -29,6 +32,24 @@ class Roles:
 
     def _nest(self):
         """nests the roles (creates roles hierarchy)"""
+        for roleid in self.roles_raw:
+            role = self.roles_raw[roleid]
+
+            # Display name is mandatory
+            if not 'display_name' in role:
+                raise MissingKey('display_name', role, self.role_file)
+
+            # Backend is mandatory
+            if not 'backends' in role:
+                raise MissingKey('backends', role, self.role_file)
+
+            # Create the list of backends
+            for backend in role['backends']:
+                self.backends.add(backend['name'])
+
+            # Create the nested groups
+            for roleid2 in self.roles_raw:
+                role2 = self.roles_raw[roleid2]
         self.roles = self.roles_raw
 
     def write(self, out_file):
diff --git a/tests/cfg/roles.yml b/tests/cfg/roles.yml
index a6ca291..fd8c9ee 100644
--- a/tests/cfg/roles.yml
+++ b/tests/cfg/roles.yml
@@ -2,13 +2,13 @@ admin-lv3:
     display_name: Administrators Level 3
     LC_admins: True
     backends:
-        - backend_name: ldap
+        - name: ldap
           groups:
               - cn=dns admins,ou=group,dc=example,dc=com
               - cn=nagios admins,ou=group,dc=example,dc=com
               - cn=puppet admins,ou=group,dc=example,dc=com
               - cn=users,ou=group,dc=example,dc=com
-        - backend_name: ad
+        - name: ad
           groups:
               - Domain Users
               - Administrators
@@ -17,32 +17,32 @@ admin-lv3:
 admin-lv2:
     display_name: Administrators Level 2
     backends:
-        - backend_name: ldap
+        - name: ldap
           groups:
               - cn=nagios admins,ou=group,dc=example,dc=com
               - cn=users,ou=group,dc=example,dc=com
-        - backend_name: ad
+        - name: ad
           groups:
               - Domain Users
 
 developpers:
-    diplay_name: Developpers
+    display_name: Developpers
     backends:
-        - backend_name: ldap
+        - name: ldap
           groups:
               - cn=nagios user,ou=group,dc=example,dc=com
               - cn=developpers,ou=group,dc=example,dc=com
               - cn=users,ou=group,dc=example,dc=com
-        - backend_name: ad
+        - name: ad
           groups:
               - Domain Users
 
 users:
-    diplay_name: Simple Users
+    display_name: Simple Users
     backends:
-        - backend_name: ldap
+        - name: ldap
           groups:
               - cn=users,ou=group,dc=example,dc=com
-        - backend_name: ad
+        - name: ad
           groups:
               - Domain Users