Sure, you can always convert traditional IRA funds into Roth IRA funds, so long as you pay taxes on the distribution. The amount converted is applied towards any minimum required distribution (MRD) as well. The requirement on "earned income" only applies to putting new money into an IRA. Conversion simply moves existing retirement account money around.
I recommend looking at IRS publications 590-A and 590-B for details. They may be found by searching in