Note that the roots will not necessarily be in any special order. So when you do plot them in sequence with p, things may jump around.
One idea would be to convert the sequence of polynomials to a sequence of 4x4 matrices. This is called the companion matrix. you can find that in the function compan.
help compan
Then use my eigenshuffle utility (found on the file exchange) to resort the eigenvalues to be in a consistent order.
Finally, do as Star suggests, and plot the real part on the x axis, and the imaginary part on the y axis.
