Access Virtual Server Roundcube from Sub Server domain

Hello Support,

First of all , Virtualmin is the best tool I have ever used, Really appreciate the team for its efforts.

I am using Virtualmin GPL on my Debian Linux,

I have setup everything successfully,

Only small glitch which I am trying to overcome

I have created my first virtual server , lets say VIRTUAL SERVER V1 as virtualserverv1.com

now I have created a sub Server S1 , i.e subservers1.com under the Virutal server V1 Then I created an emailbox for the subservers1.com as testuser@subservers1.com

I can access the mail using the URL : webmail.subservers1.com the built in app UserMin loads successfully.

How do I access the roundcube which resides within the Parent Virtual Server V1 I installed it in the location virtualserverv1.com/roundcube

I need to access it from the sub server domain subservers1.com how do i do it please?

Thanks