My roundcube email is linked with Bluehost, who is my web host. On the cpanel, go to "email", then go to "account filtering." Follow the steps for awesome filtering!
I have my filters set up to read certain words in the "subject" line of the email, and then deposit the email in their respective folders. For example, if I have [resume] in the subject line, then I will have a folder named "resume." Then I set up the Rules like this: subject contains [resume] Action deliver to folder resume.