sternpat,
You can rollover your 401(k) to a Traditional IRA and fund a SEP IRA for yourself now that you are self-employed (or a Roth IRA if eligible, or both).

Francisco,
IRAs cannot be rolled back into 401(k)s. You can rollover an old 401(k) into a new 401(k) plan if your new employer's plan allows it. (There are pros and cons to this though.)
You can however, 'roll back' withdrawn funds out of an IRA if the funds are deposited back into the IRA within 60 days of the initial withdraw, without penalty. Check out http://www.investopedia.com/articles/retirement/06/rollovermistakes.asp?viewed=1 for more info on the "60 day rule."

Can a IRA be rolled back over to a 401k?

Hi sternpat,

Generally speaking, I am a fan of rolling over 401k plans into IRAs once one leaves their employer. IRAs have much greater investment flexibility and often allow for far lower expenses than 401k plans.

The main disadvantage of such a rollover would be losing the option to borrow against your 401k. Since such loans are generally inadvisable, and since there are ways to withdraw funds from IRAs with little or no penalty in the event of a financial emergency, I don't see this disadvantage as significant in most cases.