The root locus diagram shows the evolution of the closed loop system
poles when varying a certain parameter, usually a gain (proportional
controller).
In a siso system this can be done intrinsically. In a generic
state-space equations system this is not straightforward unless the
system has one input
and one output.
If this is the case you can drawn the same root locus by constructing
the transfer function and then drawing the root locus.
(num,den) = ss2tf(A,B,C,D)
rlocus(num, den);
best wishes,
Ramon