If "nowadays many people roll.... into a ROBS account", then many people are idiots. None of MY clients are doing that.
I'm not going to definitively answer your question, because I'm willing to bet there are other problems with this "plan". Anyone who takes their qualified plan money and buys into these ROBS schemes deserves everything he gets for being an idiot (in almost all cases). It's not his fault that he's an idiot (since most of us are investment idiots), but his being taken advantage of without getting appropriate legal advice IS his fault. See the attached IRS memorandum on ROBS. Each one that the IRS investigates violates at least one and often many rules about QPs.
So, IF there becomes a bankruptcy case, a smart lawyer for the creditor is going to investigate the ROBS and find the flaws and argue there is no protection because the plan is not a "good" plan in the first place.
Your question actually anticipates that there is something about ROBS that is problemattic. The real question (that you didn't ask) is "is a 401k retirement plan protected or exempt from personal bankruptcy" and you should know the answer (generally, of course it's proteccted). The question you are really asking is whether a ROBS is a "good plan", and I wouldn't want to have to defend that client who adopted one; I want to be on the other side explaining to the judge all the problems with that plan and why it should not be given ERISA protection!
Best of luck.
Guidelines_regarding_rollover_as_business_start-ups.pdf