Yes you can. You can make this conversion if you have severed employment where you have the 401k, or if you have reached a certain age as specified in your plan, usually age 59.5 . There are no income limitations. It is a taxable event, so you will have to pay income taxes on the amount you convert into your Roth IRA. Then when you take the money out, it is tax free. Pay taxes when you convert, withdraw tax free.