While there obviously isn't any sort of "IPB integration" as of yet, I just ran a standalone of the beta client within its own folder and provided links to it within the IPB menu system(s). The Roster's "look-n-feel" will be customized to conform with the default skin at some point in the future.
Since the 2.0 Roster is still beta, I haven't fiddled with avatar/sig forum integrations yet. In fact, the only addon I'm currently using w/Roster is Armorysync, which (for the most part) is working.
What would be awesome IMHO would be portal block integration. What I'm really hoping to do would be showing (using a portal block) exactly what epic items were picked up by who, when, & where. Being able to customize the portal block's data points would be ideal.
Anyway, I just wanted to indicate that while there may not be an IPB "integration" , there are workarounds that can make the Roster work for you.