After months of obtaining contradictory advice and suggestions by various 'professionals' I believe I finally have the answer to this dilemma...since daytrading brokers only offer SEP IRAs and Roth IRAs, how do you go about setting up a Roth solo K account for trading? Apparently the answer is that you set up a solo K account as a trust. You are the trustee, as opposed to when you open a retirement account with Fidelity for example, Fidelity would be the trustee. The initial suggestion I had been given was to open a Roth solo K with Fidelity or some other outfit, then convert that account to a Roth IRA, then rollover that Roth IRA into your daytrading broker. I think this is doable, but I couldn't even get the IRS to tell me whether converting from a solo K to IRA is legal. (There has to be a 'triggering event' such as turning 59 1/2, loss of employment, etc. to get funds out of a qualified plan). The issue is, can you arbitrarily close a qualified plan whenever you want to? Is that in itself considered a 'triggering event'? I got plenty of people telling me yes, and just as many telling me no.
That's how I got the wrong idea in the first place. Probably would have gotten the right answer sooner if I hadn't.
Futures trading requires a company such as mtrustcompany.com (your broker will know this) you cannot be your own trustor in futures trading.
You can get a brokerage account with a 401k...it just has to be in your plan document. The only contribution money that can be put in the roth account is the deferral money, not the profit sharing component.
Last post on this, hope this helps...speak with your cpa. http://www.irs.gov/retirement/article/0,,id=156204,00.html