Even before tip-off, Ainars Cukste's team knew it had no chance of finishing in fourth place - the last on offer for a spot in the Eighth-Finals.
Gambrinus Sika Brno lost their game at home to MKB Euroleasing but they will advance to the play-offs ahead of Riga on a tie-breaker.
In Riga's win over the French side ESB Lille, Belarus international Tatyana Troina scored 26 points.
ESB opened up a 60-55 lead early in the fourth quarter but Riga scored the next 14 points to go in front for good.
Geraldine Robert finished with 17 points and eight rebounds for ESB Lille, who finished last in the group with three wins and seven defeats.