You can meet a lot of nice people that way. Someone on the rollcall board usually organizes a meeting place the first full day at sea, and everyone gets together, maybe at a bar area or elsewhere. By the time you go on the cruise, you will feel like you know some of the people from chatting back and forth with them. We are planning a South America and Antarctica cruise in Feb., and through our roll call, 12 of us have already organized a private group tour at Ottway Bay in Punta Arena. In case you check our Feb. 19 Star Princess board, I use a different name on cruisecritic, as SD cruiser was taken already. But checking that board will give you an idea how well a roll call board can work for everyone.
Wish we could do the same here, but it does not work. Cruise-chat is a very nice site with friendly people, and I like to spend some time here too, but it just does not have a broad enough base for roll calls for a given sailing.