In roller skating, the circles are standardized. Everyone skates circles 6 meters in diameter for the big figures and 2.4 meters in diameter for loops. This means there is no need for a scribe: the circles are painted on the roller rink floor!
This also works well because unlike ice skates, roller skates don’t leave marks. Tracing on roller skates means keeping the painted line between the wheels. The judges observe it while the skater does the figure.
American Artistic Roller Sports gives clear instructions for painting appropriate circles in its test booklet, which you can download. See pages 27–31. Scribes are usually too short to draw the big circles, but can be used for the loop circles. You’ll still need to lay down the loops themselves using the AARS technique.