mod_alias will let you add a permenent redirect to wherever you want. Doc for this directive is here
If you want to redirect your documentroot, your alias will be /
... or you can add a redirect metatag to the HTML source of your index.
<META HTTP-EQUIV="Refresh" CONTENT="0; URL=someotherurl">
Either way, the browser needs to refetch the page, so your choice. Having apache handle the redirect is better, as it will redirect *all* requests for that alias. Not just simply on one or two hypertext sources.
but... if its on the same box, why not just adjust your DocumentRoot ?????