Cyril Gane was not a proved Muay Thai fighter, this sport lacks the heavyweight division now compared to the past maybe when Ignashov, Ghiță and others were fighting in Bangkok. Gane defeated Guidon and Lentie on Muay Thai rules, who were only kickboxers close to retirement. Now Muay Thai belongs to the midgets and I feel there are even less "farangs" (foreigners, who now would prefer kickboxing instead of Thailand).
He has a notable win in Muay Thai, over the only decent heavyweight I know who is Yassine Boughanem. Basically a hamburger with no future in kickboxing.
Rozenstruik on the other hand, failed in the SUPERKOMBAT. At that time the Romania-based promotion was A, feeding K-1. And It"s Showtime disappeared, eventually Ultimate Glory/Glory appeared.
So Rozenstruik failed on the big scene. Ultimately, he did better but in China where the heavyweight divisions are below average. Did he also improve? Maybe.
Who would have won between these two? It depends also on the individual level. Rozenstruik in kickboxing was a slow heavyweight. In 2011, he KOed Adegbuyi in his first year of sport after all (without any amateur background, experience), the Romanian winning the rematch after. That win gave Rozenstruik absolutely no edge, because he was KOed by Cătinaș in 2012 and in 2013 lost to a pretty talented Bosnian Tufekčić who was training outside. But Tufekčić did not represent anything than a qualifer with some talent. Eventually SUPERKOMBAT released him and went to fight in regional leagues. WLF of China in terms of heavyweights, was also regional.