To use the Roland mill with Fusion, you need to add a machine definition. In recent versions of Fusion (as of 2024 at least) the machine is no longer in the default library.
But worry not, you can download this file containing the functioning machine definition:
To install the machine, go to the Machine Library under the Manage tab in the Manufacturing workspace and add the above file. Then you can right click → Post Process machine operations to export runnable G code.