u/DrunkLad

Going by registered rosters according to euroleaguebasketball.net during a whole season. So, for example, Zagars or Birsen are not considered rookies even tho they weren't in the 12-man roster last year. They've got "EuroLeague Champion" in their resume and it counts.

And by extension, players you haven't heard before like Grinvalds, and Talcis from this year also count.

OLYMPIACOS

• Frank Ntilikina

• Monte Morris

• Cory Joseph

• Tyson Ward

• Tyrique Jones

FENERBAHCE

• Talen Horton-Tucker

• Brandon Boston Jr.

• Onuralp Bitim

• Mikael Jantunen

• Armando Bacot Jr.

• Chris Silva

REAL MADRID

• Theo Maledon

• Andres Feliz

• Trey Lyles

• David Kramer

• Gabriele Procida

• Izan Almansa

• Gunars Grinvalds

• Egor Ammosov

• Chuma Okeke

• Alex Len

• Usman Garuba

VALENCIA

• Brancou Badio

• Josep Puerto

• Sergio De Larrea

• Xabi Lopez-Arostegui

• Jean Montero

• Omari Moore

• Darius Thompson

• Tomas Talcis

• Isaac Nogues

• Alex Blanco

• Kameron Taylor

• Nathan Reuvers

• Braxton Key

• Jorge Carot

• Jaime Pradilla

• Neal Sako

• Matthew Costello

• Yankuba Sima

Olympiacos - 5 players

Fenerbache - 6 players

Real Madrid - 11 players

Valencia - 18 players, the entire roster

Players that have been registered in a previous Final Four but never made the 12-man roster: Zagars, Birsen. I think it's only them.