You can simply turn off custom error in Web.Config, no need to use RDP. But make sure you are adding that in the root Web.Config, that will do the trick.
Here is an example:
<customErrors mode="Off" />
<compilation debug="true" targetFramework="4.5">
Just be aware that there are multiple web.configs in a typical project. Make sure you are adding this in the root web.config (where your Global.asax is) and NOT in Views folder.