By default, the basic components of your Dispo profile will be visible to everyone. This includes your profile photo, Banner Images, Display Name, and Bio.
Any photo you take on Dispo will be stored only your Library, which is viewable by you only — unless you choose to shoot directly to a roll, or choose to share that photo to a roll later on.
When you choose to create a roll, you have the option of making it Private or Public. By default, Dispo has Private toggled, but you're able to change this by tapping Public.
When a private roll is initiated, the person who created the roll is able to add members, either in-app or via the QR code. Whoever is added to that roll is then able to invite whomever they want, and so on.
Any public roll that you create, or are a part of, will be viewable on your Dispo profile by any, and all, users.