Filling out the Questionnaire is what generates compatibility scores between you and other users - giving you direction on who to network with first to find a good roommate.
If you choose not to answer the Questionnaire, you can still network with other users, chat, add friends, and find a roommate.
If you do none of the above, you'll essentially be assigned a random roommate at the end of the process.
So please take advantage of the system and use it to its full benefit!