What is the reason you have Reporting Services and the Report Server in another box? The relational engine where you are running Reporting Services needs to know your ReportServerDB and ReportServerTempDB because both are needed in processing and rendering the reports.

There are very detailed steps to move these databases if you need help on how to do it right post again because SQL Server will not render your reports if you just move the databases and the Master database does not know you have moved the databases.