There are roller derby rules even if it doesn't always seem it. With the physical contact and injury that occurs, it can appear as though roller derby takes a come-what-may approach. But, in fact, roller derby leagues around the US generally follow the rules designed by the Women's Flat Track Derby Association (WFTDA).
Roller derby rules state that each of the two teams competing may have five players on the track at once. Three of these players are called blockers (or defense), one is a pivot (the last defender) and the fifth is called a jammer (the scorer). A spectator can differentiate between the players by their helmets. Blockers have no cover on their helmets while pivots wear a striped cover and jammers wear a helmet cover with two stars.
A jam in roller derby is a two-minute period when the pack of skaters (which includes blockers and pivots from both teams) skate around the track, attempting to stop the jammers from both teams (who are starting after the pack) from getting past the pack. During a jam, blockers and pivots must stay in the pack according to roller derby rules. If a blocker or pivot is separated from the pack, she may not attempt to stop an opposing jammer or help her own until she has returned to the pack.
After the jammer gets past the pack the first time, she scores one point for each opposing blocker or pivot that she passes. Blockers and pivots attempt to stop the opposing jammer from getting through the pack using their torsos, but not their heads, hands or forearms.
The roller derby rules requires that the first jammer to get through the pack becomes the lead jammer. The lead jammer can end the jam whenever she wants by placing her hands on her hips.
Positions can change mid-jam. A jammer may remove her helmet covering and pass it to a pivot, who then becomes the jammer. However, the lead jammer cannot transfer her power; if she hands off her helmet covering to a pivot, the position of lead jammer is lost.
Penalties are incurred if a skater blocks illegally, fights or violates another rule. Four minor penalties or one major penalty result in a player being sent to the penalty box. If a skater is sent to the penalty box, the opposing team's jammer scores an extra point each time she passes the first opposing blocker or pivot in the pack.