How to run Rogue Legacy for Linux on a specific monitor?
Here are some things to try:
If the game uses SDL, it is possible to set which monitor fullscreen games will run in by setting an environment variable like so:
export SDL_VIDEO_FULLSCREEN_HEAD=0
Which you could stick into your preferred userland environment file, depending on your flavor of linux and shell.
or maybe
Adding the following line to /etc/environment.
SDL_VIDEO_FULLSCREEN_DISPLAY=0