I don't know what Ventrilo is, but if by 'roms' you mean old games that you run in emulators, there are plenty of those around for Linux. Similarly, there are plenty of media players about. Whilst you could not just run .exe files, most modern distributions have an easy to use package managing tool where you can search for applications, click a check-box and then install them. For a basic user with no specific requirements, there is no reason why a Linux installation should not work for them.
As stated already, a live CD would give you a feel for how the operating system is (but please don't make judgements based on speed in a live environment - you're reading most things from a CD and so obviously it won't be as fast as an installed system). It can also give you an idea of whether or not all your hardware will work with the system or not. Back in the day, this was particularly important for things like wireless, but that seems to be a rare issue these days - a lot of the mainstream distributions (Ubuntu, Fedora, Mandriva, openSUSE etc.) recognise and select the appropriate driver for most wireless adapters these days