How to find the camera angle of a player in first person?

So I know in 3rd person you can get the position of the mouse, but in the first person, the mouse is always in the same spot. How could I find the angle of their camera? I tried this.

while true do
    print(script.Parent.Camera:SetRoll(math.pi))
    wait()
end

But that doesn't work, how could I get the first-person camera angle?