If you mean report viewer, Crystal Reports or Reporting Services - you can use ASP.NET MVC and run reports on ASP.NET page. They can live side by side. In my current project I do just that - all of the application is MVC except for the reports viewer page. This is inside single IIS application - I use local web.config for few tweaks. But you can also dedicate a separate IIS app solely for ASP.NET reporting if you can't/don't want to run ASP.NET reports inside ASP.NET MVC applications.
I also found that sometimes generating reports in ASP.NET MVC as PDF documents and dynamically showing them inside iframe may be a better solution (cleaner and more printer-friendly for users).