I have several TeX vs. troff/groff questions and surely there are experts on here that would know both. Not wanting to have a question rejected/closed due to the *roff nature, are these acceptable questions?
There being people here who will be able to answer your question doesn't make it a good question. But that's not to say that it wouldn't be acceptable. I don't know the answer to that one. I would try an experiment. Pick one of your questions and ask it. In the question:
Explain that it's an experiment and that people are encouraged to discuss whether or not it is acceptable here (link to this specific question). That shows, amongst other things, that you're trying to play by the rules but aren't sure what the rules are, rather than are trying to game the system.
Try to make your question as TeXy as possible. Try to make it so that someone who doesn't know about troff/groff could still learn something from the answers to your question.
I'd like both troff/eqn and Postscript to be in a special category of questions that are narrowly speaking off-topic but welcome here because we are friendly.
We might have a section in the FAQ along the lines of:
Q: I know my question about digglefying grobnits is off-topic, but I can't think of anywhere better to ask it. Can I ask it here, please?
A: It sounds like it isn't really in scope, but since it seems to be to do with DIY-ethic document preparation, we will probably like answering your question anyway. To be more specific, we are happy to adopt troff/eqn and Postscript questions, and probably many other questions, but you will have to make allowances for our Tex-centric preferences.
My understanding (which may have been incorrect) was that "friends" in the site name was intended to refer to all the different variants and distributions of TeX and its derivatives (Context, Luatex, XeTex, tetex, etc. etc. etc.) as well as programs that are specifically designed to be used along with them, e.g. BibTeX, compilation managers like Latexmk, or editors like TexShop or Kile. From what I've heard about *roff, it does not fall under that category.
Of course, just because a question happens to involve some subject matter besides *TeX itself doesn't automatically make it inappropriate. I'd agree with Andrew Stacey's advice about trying one as an experiment.