With UMMC Ekaterinburg having won their game earlier in the day against Union Hainaut to improve to 9-1 and clinch first place, Ros knew they would finish second in the standings.
Isma Canto's team only led 46-43 two minutes into the second half but then reeled off 11 straight points to take command.
Delisha Milton-Jones followed baskets by Roneeka Hodges and Jana Vesela with a three-pointer, and after Erika De Souza made two free throws, Milton-Jones added two from the line for a 57-43 advantage.
The Spanish giants pulled away for a decisive win in the fourth quarter.
Milton-Jones finished with 20 points to lead Ros while Luca Ivankovic had 21 in defeat.
Ros Casares won the battle of the boards, 48-34.
Jolly started well this season but finished dead last in the group at 2-8.
Isma Cantó, Ciudad Ros Casares coach:
"Tonight it was a difficult game for us, especially mentally. Now, we are going to play against Broker Kosice, which it's a very good team and it will not be easy to win. Before thinking about playing against Spartak (Moscow Region) in the Quarter-Finals, we must beat Broker Kosice in the Eighth-Final Play-offs."
Stipe Bralic, Jolly JBS Sibenik coach:
"We played well in Valencia, better in the first half. In the second half we had more problems to stop the local's offense. When Luca Ivankovic fouled out the game was effectively over for us. We lost the game, but I'm very happy with my players because tonight they played very well."