You may start roleplaying immediately. However, until you've met the site requirements of 3 posts (which it looks like you haven't - 1 more to go), and have waited the full 24 hours since you joined, you're unable to send the initial messages when interested in RPing with someone on the site.
I suggest creating a Request Thread of your own, listing your likes, dislikes, and current cravings, and let interested parties come to you.