Weather your funds are in a 401(k), Traditional IRA or ROTH IRA doesn't matter. Those funds are managed for exactly what they are - retirement funds. All withdrawals are reported to you on a 1099-R. What you do with those funds doesn't matter and the IRS doesn't care, so log as you pay any taxes due on the withdrawals, if applicable. So if you are using your withdrawals for a business, that's a completely separate issue having nothing to do with where that money came from.
