Considering our max bet is 2,000,000 ethos (2.00 eth) there is no way for a high roller to lose 3 btc in a single bet.
But of course, if in the exact round he is playing he doesn't cash out before the game crash, he will lose his bet (not his entire balance of obviously).
There is also another possibility: if someone is max betting without cashing out, but the game is high enough, he could hit the max profit (currently at 115 eth) and win that specific round.