I'm not sure whether you can do it with the new 2005 XML PATH/ROOT features but it's certainly possible using the more complicated (but more powerful) XML EXPLICIT as follows:

SELECT 1 AS Tag,

NULL AS Parent,

GETDATE() AS 'root!1!timestamp',

NULL AS 'object!2!name',

NULL AS 'data!3!field1'

UNION ALL

SELECT 2,

1,

NULL,

name,

NULL

FROM sys.objects

UNION ALL

SELECT 3,

2,

NULL,

name,

type

FROM sys.objects

ORDER BY 'object!2!name', 'data!3!field1'

FOR XML EXPLICIT