From Bulbapedia, the community-driven Pokémon encyclopedia.
The Pokémon Wheel in action
Neon Colosseum (Japanese: カジノシアターコロシアム Casino Theatre Colosseum) is the fourth Colosseum in Pokémon Battle Revolution. The battle theme is Fortune Battles. The Colosseum Leader is Rosie. Like most other Colosseums, there are 7 battles in all.
Neon Colosseum is located on a balcony high atop a building in the middle of Pokétopia. It appears to be enclosed in plexiglass. Battles here are depicted as taking place in the middle of the night. However, the Colosseum is lit by rotating spotlights all around. In addition, lights surround the Colosseum, attached both to the outside balcony and the inside walls. As its name suggests, Neon Colosseum has many neon lights. Behind the arena is a giant roulette wheel, known as the Pokémon Wheel (see below).
The battle theme, Fortune Battle, is unique and, if the player is not good at it, frustrating. Before the battle starts, both Trainer's Poké Balls are put on a roulette wheel called the Pokémon Wheel. Each Trainer is given four Poké Balls. When the player starts the Fortune Wheel up, it will spin around until the player drops a ball onto it. The player must use the Pokémon the ball lands on as their first in battle, no matter whether it is theirs or their opponents'. The other Trainer also drops a Poké Ball, and then the player, until all four Poké Balls, or three if it is a Single Battle, have been dropped. Therefore, it is a good idea to use Rental Pass Pokémon, as opposed to strong Custom Pass Pokémon, in case the player's opponent gets the player's Pokémon. This Colosseum, with the Level 30 open rule, will round up the player's Pokémon's levels to match their highest leveled Pokémon.
After the player beats the game, they may select the Level 50 All rule. The rules do not change.
Beating Neon Colosseum for the first time in Level 30 Open mode gets the player Pikachu Gloves, a custom battle pass with Neon Colosseum in the background, 46 items in the shop, and 325 Poké Coupons. Beating Neon Colosseum for the first time in Level 50 All mode unlocks 24 pieces of gear in the shop. Also, when the player beats Rosie for the first time in Level 50 All mode, they obtain her Roserade outfit. There is a small chance of Rosie wearing a Shiny outfit when battled in Level 50 All mode. If the player beats her while she is wearing a Shiny Roserade outfit, they will obtain a Shiny Roserade outfit of their own.
The default mode of battle here is Double Battle. An option to change this to Single Battle is unlocked after beating Rank 1 for the first time.
Interestingly, Colosseum leader Rosie's Pokémon are the only ones that are set. Her Pokémon are as follows during Level 30 Open, Rank 1: