There are plenty of roms available, just not any in rom manager. Rom Manager is not as useful for the D2 as it was the D1. The only thing I use it for is to restore a backed up rom. For everything else you can just use Clockwork recovery with Bootstrap installed of course.
why they are not in rommanager - is because you need a host server to directly download from, not a third party server.. at least that is my understanding. Their is also way more roms for the d1. Someone correct me if i am wrong
You can use a third party server, but it can't handle mediafire links, and other such mass-download services. It needs direct links, the kind that start downloading as soon as you click them.