When using libraries or frameworks you will often have large portions of well-tested third party code that is unlikely to have caused an error for you. In order to keep the focus on your code Rollbar will collapse stack frames from third party code.
To set this up all you have to do is configure your SDK to send the server.root, or the prefix URL for all in-house stack frame filenames. Any code from outside the server.root directory will be collapsed by default when you load that item in the Rollbar UI.
For example, in a hypothetical stack trace with lines from the following files:
and with server.root set to /home/deploy/www/app, the lines from the vendor directory would be collapsed together, to allow you to focus on your code, and not the unlikely possibility that webfmk has a bug.
Sometimes you'll have split your code into multiple sibling modules adjacent to folders you do not want included as project code (vendor, models, controllers, for instance). In these cases you can send additional application roots in the project_package_paths key. These paths should look identical to the server root (the beginning of a URL), and the key should be in an array containing any additional folders to be considered "in-project".