The Win+Shift+Arrow keyboard shortcut can be used with multiple monitors, and it moves a window to a different monitor. The issue is however, when you have the Roblox game client fullscreen, and use this shortcut, for example to move it to the right monitor (Win+Shift+RightArrow), it just makes the client window disappear.
However, if you unfullscreen and then try the shortcut it works normally.
System Info:
Windows 11