I just finished setting up a Roundup instance a few weeks ago.  Everything went pretty smoothly until I tried to log in.  After a long time debugging (more than an hour, hacking the roundup code, inserting print statements to trace execution) I found that I had misunderstood the tracker "name" option.  This is really poorly explained in the documentation, IMHO.  Worse, when set wrong Roundup did not produce any errors, it just won't let me login.

Note that I was using roundup-server as the web interface.  I think the source of the problem is that roundup was issuing a redirect instead of displaying an error or setting the login cookie.