Unix crontab root, sys and adm

I know what the Unix crontabs do and users "root", "sys" and "adm" have their own crontab files, which are located under /var/spool/cron/crontabs. However, if I have set up a crontab task, I don't know which file should be go, root, sys or adm? Also different user's crontab job has different directory access priviledge. For example, a sys crontab command may not be able to dump log files owned by root and etc.