Since noone else from Bentley has responded...
There are basically 3 major Civil design solutions inside Bentley Systems, Inroads, GEOPAK and MX Road.
I am mostly familiar with Inroads and GEOPAK (PowerCivil in America is an offshoot of GEOPAK Site).
If you are on Select and using the latest versions of these products you will see new tools that are common in all 3 , such as Round a bout design, Civil Accudraw, Civil GPS. Roadway designer is now in both Inroads and GEOPAK (not sure about MX).
I clear roadmap for these products has been laid out at various Bentley conferences. Your best bet would be to contact Bentley Sales 1-800-BENTLEY and speak with an account rep.
Currently only GEOPAK Site and PowerCivil contain Site Modeler. This is not to say site design cannot be done using the other software Bentley offers. It is however the most dynamic modeling tool specific to site design currently offered.
Feel free to email directly if you would like to see a brief demonstration. email@example.com