Guys and girls are both welcome to be referees. Referees are required to wear skates and safety gear (though mouth guards are optional for refs), so should prepare as new skaters. As a ref you get to wear the cool zebra stripes and wave your arms in wacky ways. You can check out the roles at a bout here.
Since our refs start out as new skaters they also get to start out in Fresh Meat and get comfortable on skates calling penalties and the like. You also get to learn other officiating roles by participating as a Non Skating Official (NSO) at training and get on-the-job experience. This makes sure our bouts are fair and smooth.
If you want to check out the rules and gain the upper hand on the official hand signals please check out the WTFDA website.