I'm not sure I understand the question.
All users on the RAQ can have their own cronjobs loaded into the cron table independently of the /etc/crontab/daily, hourly etc. entries.
It's a lot easier to visualise if you install Webmin . You can then see all the cronjobs on the system, when they run and who 'owns' them
The file /etc/crontab is the system level cron file that actually runs the jobs that blacknight is referring to (those inside /etc/cron/, e.g. /etc/cron/daily/ etc).
To modify this file you do not use the crontab command, but simply edit the file directly. To quote the cron man page "cron need not be restarted whenever a crontab file is modified", so there's no need to restart cron if you do change it.
In addition, as you mentioned, root (as a user) can have its own crontab file which you should edit through the crontab -e command. These files are stored in /var/spool/cron/
The following are your friends :