In the Clone Wars Animated Series, Tyranus went to look for an apprentice on the world of Rattatak where eventually he found Asajj Ventress. Here is a roster of all officially confirmed gladiators that participated in the battle ...

Sources: Official Databank & Clone Wars Animated Sticker Book

"What we do in life echoes in eternity."

Blue Anchor - Species: Houk - Homeplanet: Lijuter
http://www.starwars.com/databank/character/anchorblue/index.html

Asajj Ventress - Species: Unknown - Homeplanet: Rattatak
http://www.starwars.com/databank/character/asajjventress/index.html

Blorga - Species: Gamorrean - Homeplanet: Gamorr
Uses a double-spike hammer.

Bugnaught - Constructor: Unknown
Humanoid Droid with bug eyes.

Carl - Species: Shikitari - Homeplanet: Shikitari
http://www.starwars.com/databank/character/carl/index.html

Crockagor - Species: Unknown - Homeplanet: Unknown
Green guy, uses huge spiked mace.

Flalios - Species: Human - Homeplanet: Unknown
Human uses chains.

Giant Flog - Species: Gorax (*) - Homeplanet: Endor (*)
http://www.starwars.com/databank/character/giantflog/index.html

Grunda Dolma - Species: Aqualish - Homeplanet: Ando

Jasper McKnives - Species: Kajain'Sa Nikto - Homeplanet: Kintan
http://www.starwars.com/databank/character/jaspermcknives/index.html

Krutch - Species: Unknown - Homeplanet: Unknown
Spiderlike creature, uses a net to trap people like a retiarius in ancient Rome

Kulltu Kutta - Species: Unknown - Homeplanet: Unknown
Brown guy with a scimitar, rides a creature calles Sowsquatch

L8-L9 - Constructor: TaggeCo
http://www.starwars.com/databank/droid/l8l9/index.html

Nilo - Species: Rodisar - Homeplanet: Rodis
http://www.starwars.com/databank/character/nilo/index.html

Mantoid Droid - Constructor: Unknown
Black droid with many appendages

Swyy'm-Ee - Species: Trigodile - Homeplanet: Rattatak
Crocodile like alien, uses two large knives called fi'lang.

Unknown gladiators:
- Wampa
- Roman style gladiator

(*) The fact that Giant Flog could be a Gorax is entirely my own assumption and is not confirmed. I based that because his owner obtained him on a trip to the Moddell Sector where Endor is situated.