Adding List for Roles

Change-Id: Idea3ec6f3c7d74c4b754c4c143199a58a4855738
diff --git a/openstack/identity/v3/roles/requests.go b/openstack/identity/v3/roles/requests.go
index 8d701c0..3d7c179 100644
--- a/openstack/identity/v3/roles/requests.go
+++ b/openstack/identity/v3/roles/requests.go
@@ -5,6 +5,14 @@
 	"gerrit.mcp.mirantis.net/debian/gophercloud.git/pagination"
 )
 
+
+func List(client *gophercloud.ServiceClient) pagination.Pager {
+	url := listURL(client)
+	return pagination.NewPager(client, url, func(r pagination.PageResult) pagination.Page {
+		return RolePage{pagination.LinkedPageBase{PageResult: r}}
+	})
+}
+
 // ListAssignmentsOptsBuilder allows extensions to add additional parameters to
 // the ListAssignments request.
 type ListAssignmentsOptsBuilder interface {