<a href="http://help.roll20.net/mobile-support/" rel="nofollow">http://help.roll20.net/mobile-support/</a>
While I do not use a mobile device myself it is my understanding that it requires Chrome rather than an App. Assuming you have a reliable means to connect your Android to the internet and the particular Android you are using is powerful enough then you should be able to use Roll20.
- Gauss