Thanks for inquiring Aspose.Slides.
Our development has investigated the requirements for applying the template on generated presentation. PowerPoint template represents set of slides with predefined layout and formatting and the presentation template are applied on placeholder added in layout slides. When reports are exported using Aspose.Slides for Reporting Services they are not placeholders. So, this way the presentation template cannot be applied to exported content. It’s not obvious how to mix template layout with report layout because RDL doesn’t have concept of placeholder.
So, can you please share more details in terms of expected results from applied template and we will see whether that requirement is possible or not.