Roll20 is described as 'The free, easy way to play tabletop games (such as pen and paper RPGs) online with others. It's completely web-based, so it runs right in your browser. It supports video and voice chat, background music, character sheets, a massive art library, and more!' and is a virtual tabletop in the games category. There are more than 50 games similar to Roll20 for a variety of platforms, including Web-based, Windows, Android, iPhone and Linux apps. The best Roll20 alternative is MapTool, which is both free and Open Source. Other Roll20 like games are Fantasy Grounds, Foundry Virtual Tabletop, Meridian Realms AI and DiceRight.
DiceCloud only tracks some character sheet details; Roll20 offers all sorts of tools to assist gameplay, from handout tracking and sound effects board to featureful tabletop simulation and all sorts of aids for gameplay mechanics, from ability and skill checks, to combat rolls, and even spell casting… these two tools are not remotely comparable.