I want to add descriptions to database roles in SQL Server and have used sp_AddExtendedProperty to add an MS_DESCRIPTION property to various roles but DocumentX does not seem to pick these up.

It works fine for tables and fields but not for any other object.  Has anyone else had any luck with this?

At present, the description extended property is only read for the items for which there is a built in UI within the SQL Server management tools to define them - tables, fields, views, procedures, functions. I have logged a feature request for a future update of Document! X to enable reading of extended properties from other object types too. Sorry I couldn't be of more help at this time.