ROI imports files up to 100MB. For files over 100MB, we recommend the files are split before import. For example, if you want to import 1GB of data we recommend that you split the file into at least 10 parts (100MB each) and then upload the ten files with similar naming conventions. If your file naming convention begins with Contacts, then you could create all ten files with a naming convention that starts with Contacts: Contacts1.csv, Contacts2.csv, Contacts3.csv, Contacts4.csv, Contacts5.csv, Contacts6.csv, etc.