Note: this project is effectively abandoned. It may serve as a useful reference at times, but it's not being kept up-to-date. The last thing you should do is fork it to make your own compositor and you certainly should not package it for your distro.
If you are looking for a better reference or jumping-off point, check out tinywl. There is also a list of resources for getting started with wlroots available, as well as a list of other projects using wlroots, whose code is likely a better reference.
Historical readme:
Rootston is the "big" wlroots test compositor. It implements basically every feature of wlroots and may be useful as a reference for new compositors. However, it's mostly used as a testbed for wlroots development and does not have particularly clean code and is not particularly well designed: proceed with a grain of salt. It is not designed for end-users.
If you followed the build instructions in ../README.md, the rootston
executable can be found at build/rootston/rootston. To use it, refer to the
example config at rootston/rootston.ini.example and place a
config file of your own at rootston.ini in the working directory (or in an
arbitrary location via rootston -C). Other options are available, refer to
rootston -h.