Ekaterinburg, who were pushed to the limit by Ros in the first meeting back in Russia and only won in overtime, crashed to a 71-63 defeat to Isma Canto's team.
Ros Casares (6-2) stamped their authority on the contest from the beginning and led the entire way.
By the end of the opening quarter, they had a 25-10 stranglehold on proceedings.
The home side extended the lead to 36-18 by half-time and stretched it to 51-29 in the third quarter.
They were still on top 55-40 at the end of the third and cruised in the fourth, with Ekaterinburg making the scoreline more respectable at the end.
Amaya Valdemoro and Delisha Milton-Jones wreaked havoc on the Russians.
USA Olympic gold-medal winner Milton-Jones scored a game-high 19 points and Spain's Valdemoro had 18 while Sandrine Gruda of France poured in 18 in defeat.
Ros Casares made 13 of 16 (81.3%) attempts while Ekaterinburg managed to sink just eight of 15 (53.3%).
Poland national team star Agnieszka Bibrzycka has been arguably Ekaterinburg's best player this season but she missed all five of her shots from long range and finished with just four points.
Deanna Nolan also had a nightmare night, making just one of 10 shots and finishing with five points for Ekaterinburg.
Isma Cantó (Ciudad Ros Casares coach):
"Tonight we showed Europe that we are a competitive team, against one of the three best teams in Europe. Our first half was incredible, but we had problems in the second half to play at the same level. The game was very positive for us, because we have secured second place in the group."
Laurent Buffard (UMMC Ekaterinburg coach):
"Our team started the game against Ciudad Ros Casares without a good mentality, I guess we were too 'cold' to play in Valencia. In the first half we had too many turnovers and our shooting percentage was terrible. In the second half we tried to play better but the gap was too big."