For official answers always ask through the forums or
frcteams@usfirst.org
Unofficial answer:
You do not need to register for the purposes of consideration of rookie awards. But you will need to register if you are submitting for Woodie Flowers and Website submissions.
If you chose to complete a Chairman's Award submission, you can register, go online, fill out RCA form, and print it out for your records and to give to judges in the pit. The judges will not see the rookie RCA submissions online.
Or you could follow the guidelines in the link in the post above to prepare a "Chairman's - like" submission and give to the judges in the pits.
There are no current requirements to compete for rookie awards. But the more ways you can help the judges understand your team, the better it is.
Don't forget to also complete the "Judges Information Page."