I have done something like this by adding a Store Catalog module to a separate page for each category / role I want to support. I default each Catalog to a category that matches a DNN role. I then control access to a given category by granting access to the DNN page containing its Catalog (defaulted to that category).

I have not yet tested this setup with the current release, but it worked for me a version or so back. Initially there were issues with the links on each Catalog page but once those were resolved I was able to have a separate Catalog for each of my clients within one Store.