What are the webxroll.NN and webxdb.NN files in my root webx directory?
These are Web Crossing generated backup files. Webxdb.NN is a snapshot of the web.db file at the time of the last backup. Webxroll.NN files are "roll forward" files which accumulate all changes made to the database since the last backup. In the event you need to restore your database from backup, the roll forward file is merged into the webxdb.NN so that your database is brought current.
See your documentation or other FAQs for more details.