Like adding files, removing files is done in two steps: First, the files have to be registered as removed by choosing → or right clicking the marked files and choosing from the context menu. The CVS Remove dialog will appear, listing the files you marked, and asking for confirmation. Press . Cervisia issues the command
cvs remove -f
After that, this modification to the sandbox has to be committed, possibly together with other modifications to the project.
The above command only works if the file is up-to-date. Otherwise, you get an error message. This behavior is sensible: If you have modified the file compared to the version in the repository, or if someone else has made any modifications, you will first want to check if you really want to discard them.