You need to iterate through what roles.query() returns, also don't needs quotes around role, but you do around change_management. So I think your code should look like this:

roles.addQuery('user', userID);

roles.addQuery(role, 'change_manager');

roles.query();

while(roles.hasNext()){

         if(roles == 'change_manager'){

                   return true;

         }

         return false;

}