If "y in x" means the rise is y for a run of x (both in the same units), then the tangent of the angle is y/x.
... angle for 4 in 4 roof: arctan(4/4) = 45°
Yes, it is possible to have a 7 in 4 roof.
... angle for 7 in 4 roof: arctan(7/4) = 60.3°
_____
As long as the run is non-zero, the rise can be anything you like.