geoffw (see below) is quite right about what happened to this show: poor network marketing support (complicated by network interference with the concept). The Christian Right had nothing to do with its cancellation, and the individual who suggested that is out of touch with the facts.
The fact is that this was another wonderfully original and well-developed concept from Shawn Cassidy (who also created 'American Gothic', among others) that was mis-marketed by FOX. Apparently FOX wanted to grab some of the riches generated by camp sword and sorcery shows like 'Hercules: The Legendary Journeys' and 'Xena: Warrior Princess'. They gave Roar very little marketing support (I remember vague promos showing people in leather armor that gave no idea what the show was about), and what little support they did give it implied it was a Hercules/Xena clone. It wasn't. When the wrong audience tuned in and rejected it, FOX started moving it all over the schedule, again without proper marketing support. They also applied pressure to the producers to dumb it down and make it more like Hercules/Xena. Watch a marathon on Sci-Fi sometime, and you will notice the following network-inspired trends:
1) The importance of Conor's struggle to unite the Irish clans diminishes. By the middle of the series, his efforts in this regard are only described in throwaway dialog and aren't seen on screen. These efforts should have provided the meat of the series. What table scraps we do get imply that the mission was effortless, which it certainly would not have been (clan rivalries historically prevented the Irish from uniting for the common good, which is how the English got a foothold centuries later). We frequently see Conor and Fergus travelling aimlessly about doing good deeds (instead of raising a resistance against the Romans) ala Hercules and Iolaus.
2) The importance of Conor's war band withers over the course of the series, until finally they don't even appear -- even though they are still credited as regular characters. By midway through the show's run, we usually see Conor and Fergus travelling alone, despite the fact that Conor is an important king who should be regarded as a deadly enemy by the Romans.
2) Vera Farmiga's costume becomes smaller and smaller, until the introduction of Melissa George as Molly, after which the character of Caitlin is rarely seen at all. Obviously a misguided attempt to "sex it up", and when the writers couldn't distort the Conor-Caitlin relationship enough to permit romance, they introduced a new love interest.
3) Originally intensely dramatic, with tragic loves, murky intrigues, murders and double-crosses, by mid-run it had become a campy adventure comedy.
4) The character of Longinus was a well-crafted and mysterious villain with tons of potential. Unfortunately, with the tone of the show shifting, he simply wasn't silly enough, so they unsuitably disposed of the character (it violated the integrity of the character to have him fall victim to such a plot) and made the ridiculously camp Diana the sole villain.
This could have been a great show, and it didn't hurt that the cast is actually quite competent. But I suspect that -- after the failure of 'American Gothic' -- Cassidy was willing to do anything to keep his new masters happy. Unfortunately it diminished his vision, and killed the show.
Ultimately, Roar became indistinguishable from the ilk of Hercules/Zena, but because the characters weren't designed to be camp it couldn't compete with that class of show. Had FOX left well enough alone and helped it to find the RIGHT audience, we would at the very least have a great short-lived series to collect on home video. Now, we don't even have that.
