Thanks for considering Aspose.
Well, you can do both ways.
Well, Aspose.Cells for Reporting Services has two built in components. With Aspose.Cells.Report.Designer users can design a report template in MS Excel instead of Visual Studio. The report template is then embedded into Reporting Services RDL file and can be published to Report Server. Users can also preview and export the report in Aspose.Cells.Report.Designer.
Aspose.Cells.Renderer for Reporting Services is actually an implementation of Microsoft Reporting Services Rendering Extension. The renderer can render the RDL report designed by both Visual Studio.NET and Aspose.Cells.Report.Designer. To render an RDL report designed by Aspose.Cells.Report.Designer the renderer first extracts the report template from RDL file that is added by Aspose.Cells.Report.Designer at design time, interprets the template information and populates the template with data supplied by Reporting Services.
For further referenc, please check the documentation: http://www.aspose.com/documentation/ssrs-rendering-extensions/aspose.cells-for-reporting-services/index.html