Most RPG mod servers are unique, as Tribes and the RPG mod are naturally very modifiable.

If you would like me to host a particular RPG mod, feel free to contact me.

I currently host 2 RPG servers:

Phantom Worlds RPG - The primary Tribes RPG server with many unique features as well as many borrowed features. Multiple entire rpg worlds contained in a single server. Requires special client-side files (included in the Tribes Repack). Still updated constantly.
Server status: up | Top players list | Activity charts

Chrono Trigger RPG - A mod inspired by, but not officially related to, Chrono Trigger.
Top players list

In the past, I have also hosted other servers:

TvT RPG - Team vs Team RPG mod, a very different type of RPG with the main focus on fighting other players (aka PvP). The mod was mainly made by Bovidi, with improvements by Kyred and myself.
This mod will be hosted again later on, with a new map and other new features.

Farm RPG - A unique farming RPG. This mod was incomplete and did not work, eventually I gave up trying to make it work.
In a nutshell, you would create a farm, harvest crops, perhaps tend animals, mine for materials, upgrade your farm. You would be surrounded by the farms of other players, in a vast flat field. Competition was probably planned but not implemented.

Mythical Realms RPG - Mythical Realms Tribes RPG mod, with some bugs fixed. Not in active development.
This mod was notable for it's wide array of magic (elements such as fire, earth, wind, lightning). There were also added dungeons, weapons, and items. Many features of this were ported into Phantom Worlds RPG.

Redmoon RPG - RedMoon RPG mod, a special RPG mod which has many changes, requires special client-side files (included in the Tribes Repack). Not in active development, and not complete.

Quest RPG - A mod full of neat mini-games and such. Mostly by Bovidi.