Are companies that manage Roth IRAs required to report to the I.R.S. a Roth IRA owner's annual contributions, interest payments and withdrawals, or is this solely the responsibility of the Roth IRA owner when he files his annual tax forms?

While I don't know the exact requirements I can tell you that they report contributions to you AND the IRS on form 5498 and they also report distributions to you AND the IRS on form 1099.