Hi Norseman, You will not need anything to run the module that is not in the print book. You will have all monsters, maps, token art and so forth. What you will not get is anything specific to the Players Handbook. So yes, you can build player characters, but if you do not have the PHB, you will be limited to the options available in the SRD released by Wizards of the Coast: One sub race option for each race, one sub class option for each class, one background, one feat, etc. If you have access to the material in print there is absolutely nothing preventing you from adding any of that stuff manually, of course. A Roll20 module of WotC material contains every print and text resource available in the print edition of the module. Any monster only referenced by the print edition will still use Monster Manual art. Any monster you decide to add for yourself will be limited to what you have purchased or are willing to create manually. It can be a little confusing if you are new to the game, so please ask more questions if any of that was unclear.