You can set the location of the default RoboServer project folder in the 'Project' tab of RoboServer Settings. By default, the folder will be set to the default robot project created in the installation folder by the installation process. See the Design Studio User’s Guide for more information on robot projects.
The RoboServer default project is used only by the API. When executing a robot from the API, any references it has to types, snippets or other resources are resolved by looking in the default project.