No, you don't have to send a journal or labels or fabric. You CAN if you want, but really this is a "as you prefer" thing... they are suggestions and if it suits you, then do it! If not, no one is going to get upset. I am sending fabric because I used it in my center and it's unique - I'm hoping everyone can incorporate it into their borders.
I haven't figured out what I'm going to do, label-wise. I'm debating internally about making a set of blocks and asking each person to sign one; but you could go as simple or as intricate as you want. The biggest thing I can stress to you is to send a note with what you are hoping to see, what you are hoping NOT to see, if you would like certain colors, if you wouldn't like certain colors, etc.
I know that Brat and Jaba have a bit of experience doing these (the definition of "bit" is left to individual interpretation) and that Teri and Amy are both first-timers for the round-robin.
Don't stress, take your time, and enjoy this. I suppose I can't speak for everyone but I judge our group to be pretty laid back and willing to help.