ratpoison provides functionality to group windows together. This coupled with saving and restoring frames configurations is what most people would call virtual desktops or workspaces.
While ratpoison doesn't explicity provide support for such things, it
does allow you to write scripts to this end. Such a script exists in
contrib/ called rpws. Consult that file for details on
seting up workspaces inside ratpoison.
Groups are more general purpose than workspaces. windows from one group can be visible along with windows from another group. If you switch to a different group nothing changes except the list of windows you can cycle through. ratpoison allows the user to move a window from one group to another, merge two groups, create new groups, and delete existing ones. See Commands, for information on the commands for manipulating groups.