Personally, I've never heard of a file type of .HSP. What application created it?
Odds are, RoboHelp won't understand it.
It is the source file for a product called Innovasys that creates a chm file.
Sorry, but RoboHelp has no capability to import anything created using other tools aside from Microsoft HTML Workshop.
You might look and see if this tool has a file with a .HHP file extension. If so, you can likely import that to create a project in RoboHelp. But depending on how this Innovasys tool stores its content, you may not see topics come in.