Since we are dealing with a cylinder, I thought it would be wise to use the cylindrical coordinate system.
Therefore
$x=rcos\theta$
$y=rsin\theta$
$z = x^2+y^2=r^2$
Therefore my final answer would be:
$r(r,\theta, z) = (rcos\theta, rsin\theta, r^2) $
But that seems like a parmeterization of just the cylinder, without the intersection of the plane and the paraboloid.
I would appreciate any input.