So I swang by Half Price Books earlier this afternoon. I had several bags of books to sell off and they have comics I could browse through.
Among the comics I found a decent smattering of the first 30 issues or so of ROM. Including #1 for a mere 48 cents! So I picked up some of those, plus copies of Agnes Quill and the first Y: The Last Man TPB for considerably less than the books that I dropped off fetched for me.
And I got to thinking about how, if someone wanted to read the ROM stories, they're stuck hunting for back issues. The series has never been collected or reprinted in any form, in large part, I suspect, because the trademark for the character is owned by Parker Brothers, which is in turn owned by Hasbro. Which means that getting the rights to reprint ROM would be a mess of legal paperwork. Reprinting, say, any given issue of Amazing Spider-Man is non-issue by comparison since marvel owns all the rights themselves.
These days, I think just about everything first printed by marvel and/or DC has been reprinted in some fashion. And, as a rule, it's generally easier and cheaper to get the reprints than the originals. But there are a handful of books out there where reprints have never been done and are considerably less likely to be issued because of exactly the same legal wrangling.
2001 springs to mind. When I was researching those stories for Jack Kirby Collector, I knew that it had never been reprinted and was unlikely to be seen any time soon. Even though I only needed a handful of issues, and the stories were generally self-contained, the rights to at least portions of the book belong to someone else.
In some cases, the comics were trademarked by their creator and the rights were wholly held onto by them. In such cases, reprint rights would be much easier since the new publisher would only have to acquire permission from the creator or his estate/heirs. Image, for example, recently reprinted Jack Kirby's Silver Star and has plans for Captain Victory -- both originally publishing by Pacific. More interestingly, TwoMorrows has already reprinted the original Captain Victory series and the title character recently appeared in a few issues published by marvel. But in every one of those cases, usage of the character was granted expressly by the Kirby Estate, and no other legal wrangling was needed.
That's not to say things are impossible, mind you. I was actually quite surprised to hear a while back that Dark Horse was going to reprint the old Conan stories originally published by marvel. And Dell's Star Trek saw life again from Checker Book Publishing. It seems to me that both of those would've been a nightmare to work through the legal messes there, but they came through nonetheless.
That being said, though, I wouldn't hold my breath waiting for reprints of Tarzan or Godzilla comics.