Have you tried to connect to the existing installation during the setup on server A or have you tried a full install of the app-role?
You can try following config snippet for installation
<CRMSetup>
<Server>
<SqlServer>SQLServer</SqlServer>
<database create=”false” />
<InstallDir>c:\Program Files\Microsoft CRM</InstallDir>
<Roles>
<Role name=”AppServer”/>
<Role name=”SDKServer” />
</Roles>
</Server>
</CRMSetup>