Below is an example of an LDIF file to load groups that will become MongoDB roles. The distinguished name of the group will be the name of the role in MongoDB.
dn: cn=SecOff,ou=Groups,dc=waysysweb,dc=us,dc=com
cn: SecOff
ou: Groups
member: uid=ajones,ou=Users,dc=waysysweb,dc=us,dc=com
description: Users who can administer any database
objectClass: groupOfNames
dn: cn=SysAdmin,ou=Groups,dc=waysysweb,dc=us,dc=com
cn: SysAdmin
ou: Groups
member: uid=tsmith,ou=Users,dc=waysysweb,dc=us,dc=com
description: Users who can administer replica sets and shards
objectClass: groupOfNames
dn: cn=DbAdmin,ou=Groups,dc=waysysweb,dc=us,dc=com
cn: DbAdmin
ou: Groups
member: uid=aroberts,ou=Users,dc=waysysweb,dc=us,dc=com
description: Users who can administer databases
objectClass: groupOfNames
dn: cn=Dev,ou=Groups,dc=waysysweb,dc=us,dc=com
cn: Dev
ou: Groups
member: uid=akumar,ou=Users,dc=waysysweb,dc=us,dc=com
description: Users who can develop clients for the database
objectClass: groupOfNames