RFA files contain BIM (Building Information Modeling) data and require Autodesk Revit software. These files are also known as Autodesk Revit file.
DWG (from drawing) is a proprietary binary file format used for storing two- and three- dimensional design data and metadata. It is the native format for several CAD packages including DraftSight, AutoCAD, IntelliCAD (and its variants), Caddie and Open Design Alliance compliant applications.
Your RFA file can be converted to DWG by a registered CAD application. And I happen to have both AUTODESK AND SOLIDWORKS.