Can I simply right-click on the root folder where the repositories are stored and view the size on disk? Im planning on moving the repositories to a new server and checking storage space requirements. The size of the root path seems awful small compared to the working copies I have checked out. Are they compressed as they are stored on the server path?
Yes, you can simply right-click the repositories root directoiry (e.g. C:\Repositories) and you'll see the size of your repos.
In addition to this, if you want to check the size of your repositories, use Measure-SvnRepository PowerShell cmdlet. VisualSVN Server PowerShell cmdlets are available beginning with version 3.4, so make sure that your server is up to date. For information about other PowerShell cmdlets, read the article KB88: VisualSVN Server PowerShell Cmdlet Reference.
BTW, don't confuse Subversion repository with a full working copy checkout of this repository. Subversion repository use special space-saving techniques and in majority of cases it will be smaller than a fill working copy checkout of the repository. See SVNBook | How Subversion saves disk space.