The back bone of RoM is Group mechanics (tank/healer/dps) designed for instances and gear modding. So when it does come to PvP, it is typically dominated by the favored dps of the current chapter and whoever spends the most time or money.
The level matching on RoM has some pretty big jumps. If you sign up for the pvp games the lvl categories are lvl 1-14, 15-29, and then lvl 30 to current max level (atm is lvl 70). So you could be a lvl 40 facing and end-game geared lvl 70 toon and that gets pretty one-sided fast. The ability to twink/overgear lower lvl toons also means some imbalanced fights at the lower levels.
There is 1v1, 3v3, 6v6, several small group games and races, and guild battles (which are a huge favorite of RoM players). As well there are the PvP servers with smaller population and PK mode on the PvE servers but I believe it is seldom used.
Basically the core game mechanics weren't designed with PvP in mind and so RoM struggles a bit in that area. Much more fun if you are into group play and raid tactics on bosses.
I don't know anything about WoW pvp, so I can't comment there.