I think that no bookmaker can be trusted with large bets. It doesn't matter if it's a small crypto bookie or a big fiat bookmaker.
Do you really plan to bet amounts over 10K on bookmaker platform? Why are you asking for Fortunejack and Rollbit only?
There are other crypto bookies out there. I wouldn't recommend any bookie in particular, because I don't want anyone to blame me for their loss(or for their future problems with the bookmaker).
AFAIK, some bookies become suspicious when they see ridiculously large bets on certain games.
Are you really going to trust some random guy on the internet, who will say "Yeah, I was betting 10K on Fortunejack or Rollbit and I had zero problems!"? I don't trust the opinions of random strangers on the internet.