do you have the correct file location "~/.steam/debian-installation/steamapps/common/Streets of Rogue", run the command ls[list directory] you should see
"StreetsOfRogueLinux_Data StreetsOfRogueLinux.x86 StreetsOfRogueLinux.x86_64" of that run the command listed bellow "./StreetsOfRogueLinux.x86_64 -screen-fullscreen" 0
the first section selects the file(the game) and the second sets it to not full screen
you should be prompted by the game, asking if you want full screen, or not full screen when the game open