I have this problem, but I do not have root permissions because i was using web hosting.
so how can i do?
You don't need to be root to set the cronjobs. You'll need use the same user that executes the webserver.
Also, check this page too: http://devdocs.magento.com/guides/v2.2/install-gde/install/post-install-config.html#post-install-cro...
Are we still talking about cronjobs?