Help with Buck converter control

Hi everybody.. I am working on control of Buck converters presently and was wondering if someone could help me with it. I want to design a compensation controller for it so that it comes within a certain specification( Rise time =100us approximately and so on) . I have the transfer function now and was analyzing the root locus. However I am not sure about the anlaytical procedures since the open loop poles are complex ! Any help would be sincerely appreciated. Thanks!!!