The Chrono Compendium started as an archive and grew its own community. And I definitely see a community here, composed of core regulars. One can't function without the other these days. No one searches Google for "ROM hacking forum" anymore, and sites without communities eventually die out. ROMHacking.net has always looked healthy to me.
These problems are just the nature of the business. Some of the greatest fan sites have been ruined by petty, divisive leadership (OCRemix and VGMix are big examples), but the moderation here seems to be really good. It might help to make a core mission statement and charter. The Compendium has this:
The Chrono Compendium's mission is twofold. It first aims to archive and catalogue all existing knowledge and plausible speculation regarding the Chrono series, whether textual, auditory, or visual. The Compendium secondly wishes to create new content, and foster the growth and development of the Chrono series and its fan community.
Those are huge claims, but that spirit has given rise to ROM hacks, analytical articles, editorials, humorous features, community projects, art and fiction projects, guide-writing, etc. you name it. Think big with romhacking.net; ask the people what they'd like, with the core goal in mind of facilitating ROM hacking. Use your influence to make a site-wide endeavor at some point; that can REALLY foster a sense of community. I use the Compendium in some ways to involve everyone possible; Chrono Trigger: Crimson Echoes is considered THE site project, and consequently, it's had enough help over the years that it'll definitely be released before summer.
So perhaps you can make a big ROMhacking.net tutorial push, or a huge review push. Hand out special usergroups of merit, or find other intrinsic incentives. Maybe tie things together so people will have a "Review Count:" under their avatars. It's cheap, but it's not like post count in that reviews actually help the community. Controls can be implemented to prevent review spam for people who just want a big review count.
You could also use your influence to hone in on specific projects that will bring a lot of renown to ROM hacking in general, like Lenophis's FFVI hack. I'm not saying working on FFVI is inherently more important than working on another game, but people will pay more attention when a great hack for a big game gets released. So you can sort of gently push resources in that direction by contacting Lenophis, asking where he needs help on his hack (perhaps some difficult ASM work's needed that he's unfamiliar with), making some sticky threads and a small image on the front page, etc. And then voila, the gaming community hears about this great new FFVI hack, thousands of people try it out, and some people get interested in ROM hacking. I got in the game because of Temporal Flux; once I saw how easy it was to hack Chrono Trigger, I had to do something. Similarly, you could have tutorials for FFVI hacking concurrently prepared, so when these new fans come to the site, they'll say "hey, I can change stuff too," and they'll get involved.
The effects might be small, yes. Chrono Trigger: Prophet's Guile got around 25,000 downloads. But inspired at least a handful of people to come to Kajar Laboratories and try out hacking for themselves. Back in the day, the CT community was totally dependent on Geiger, JLukas, and Chickenlump. Now, a core community is doing all sorts of things, like justin3009's 6-letter name patch for Chrono Trigger, Vehek's methodology tutorial for converting custom MIDIs to MMs to SPCs for Romancing SaGa 3 and then CT, or the development of a Prerelease exploration patch (and translation once TF supports it). And while we don't answer really stupid questions at Kajar Laboratories (how do I add a 3D model to the ROM? and such), but the community does answer an awful lot of questions. Over time, this has built up infrastructure in community and archiving both.
Just flex the ROM hacking muscle with a great archive and tutorial function, and let the community come. Be friendly and encourage development. Steer resources using site-wide projects that foster a sense of community and attract attention and interest. The sky's the limit.