I assume your SSRS implementation is hosted on the same server as your application databases. If so - you can build a small SSRS only server that hosts both the database engine and reporting services and is dedicated to only reporting services. This could be nothing more than 4 CPUs and 8GB of memory (or more - memory isn't considered in licensing).
This also allows you to upgrade SSRS independent from your application. The only databases hosted on this instance would be the report server databases - which simplifies the management of SSRS.