I had a new roof put on my house in June 2011 We are not happy with workmanship We did hold back on some of the money until repairs are done

You should try to work things out wit the roofer.  You have the retention.  He has a right to file a lien.  If he does so wrongly, you may counterclaim for Slander of Title.  You can always contact the Michigan authority that licences contractors.  They probably have a mediation service.  Staying out of court is a good idea if possible.  Good luck.