Replacing Squirrelmail With Roundcube

I have Squirrelmail installed on a VPS running CentOS with ControlZX as a control panel and I'd like to replace it with Roundcube. What I'm trying to do is make it so that the Roundcube webmail application is accessible through every domain on the VPS (e.g. domain1.com/webmail , domain23.com/webmail) without having to manually install it on every domain separately. Also, because I have resellers hosted on this VPS I don't want to just install Roundmail on our main domain and provide that as the official webmail access area because then our reseller's customers would have no choice but to access their webmail via our domain. For obvious reasons most resellers would prefer to keep their provider's presence in their own business transparent.

I know Roundcube supports "virtual users" and have a basic understanding of how that works, but I am unsure how setup Roundcube so that it can be accessed from any domain on the box. Where should I install it?

I've heard plenty of users talk about using Roundcube as a replacement to Squirrelmail so I have to assume it can be used in the way that I'm talking about (that is, not needing to be installed on every individual domain manually).

For those of you that have done this, can you please describe how you accomplished it?

I also don't have a problem hiring someone to help us complete this but am still interested in knowing how to go about it.