Our company has separate openfire servers. Each on its own domain. Is it possible to share the rosters between both servers
To my knowledge, there is no way to do this cleanly out of the box. You can do some hacks with setting up the Subscription Plugin to auto-accept subscriptions, but you have to manually keep the rosters in sync on both sides.
Search around in the archives, there have been a number of posts on this previously.
There is not native way to do this with separate domains. You could use a virtual domain to aggregate the 2 real domains into one.