Rolisteam is a free and open source virtual tabletop software designed to allow users to play role-playing games over the internet. It provides a graphical interface with a variety of features to make playing games online more enjoyable and efficient. Players can use the app to collaborate on maps, characters, stories, and more, allowing them to quickly and easily share ideas and information with one another. Rolisteam also provides a rich suite of tools for game masters to create and manage campaigns, including dice-rolling, character sheets, and turn-tracking. Additionally, Rolisteam offers a wide range of other features, such as voice chat, audio and video streaming, and file sharing. With its powerful and intuitive tools and support for a wide range of platforms, Rolisteam is a great choice for any tabletop gaming group.
Fabletop has its own established rules system, while Rolisteam is an application that allows players to play their rules systems. So, for example, a D&D group could play with Rolisteam. But you don't find any functionality in fabletop.