Code B and the IRA/SEP/SIMPLE box being marked are mutually exclusive. You have an erroneous From 1099-R if this is what you received.
Code B means that the distribution is from the Designated Roth Account in a qualified retirement plan like a 401(k) while the IRA/SEP/SIMPLE box being marked indicates that the distribution is from a traditional IRA, two totally different kinds of retirement accounts.
