Hi Mike,
The product listing page in Smith Cart will use a session variable titled "SearchPID" for filtering products if it exists in session. The "SearchPID" session variable is simply a comma seperated list of product ids.
If this doesnt work for you, the Smith Search module configured for the "Single Search Box Layout" provides the following role filtering options:
All - Public and Role Secured – The “All” option will search across all products, both public viewable products and products you have defined as only viewable by DNN role.
Public Only – The “Public Only” option will allow searching of public viewable products only. Products you have defined as viewable by only certain DNN roles will be excluded from the search.
Role Only - The “Role Only” option will allow searching of Products you have defined as viewable by DNN role. Products you have defined as public viewable will be excluded from the search.
Hope this helps!