"a multi-rooted schema may not define a message part; reference the roots directly"

Using the "Add Generated Items" to add an "Adapter" for use with SQL Server in order to send data from BizTalk to e.g. a Stored Procedure, you might end up with a so-called multi-rooted schema.

This kind of schema is generated to enable a response coming back from SQL Server to be used in the Orchestration you need the message (using a Request-Response send port).

However, within the schema, you end up with 2 rootnodes. 1 for the Request message structure and 1 for the Response message structure.

If you want to promote a property within one of those structure, you could end up with the compiler telling you "a multi-rooted schema may not define a message part; reference the roots directly". This would occur e.g. if you would use a Message Assignment shape to set the promoted property to some value within your Business Process.

In order to resolve this error, make sure a "Root Reference" is selected in the generated schema pointing to the element containing the promoted property. This setting can be found on the "Schema" toplevel element in the Schema Editor view.