This assumes that Bank B actually deposited the money in a traditional IRA before converting it to Roth. If Bank B was under the mistaken impression that it was receiving a trustee-to-trustee transfer of a Roth IRA from Bank A and deposited it directly into a Roth IRA, Bank B would not have generated any Form 1099-R and the 2018 Form 5498 from the Bank B Roth IRA will not report any rollover or conversion contribution to the Roth IRA. If Bank B has already issued a 2018 Form 5498 from the Roth IRA, look at it and see what it reports.
