Hi,
well more or less. You have the Web Client as a standard way of accessing NAV from the web, and you can build a role center to fit yor needs. There are also AddOns which provide this facility. From what you write, Anveo WebDesk might be a good choice. This solution is very capable, scales well, has an offline capability for mobile devices (good thing, this), and can be completely configured from inside NAV.
Link: www.conion-media.com/anveo-web-desk-anveo-mobile
with best regards
Jens