For people looking to build a balanced retirement savings portfolio, a Roth IRA can serve as a great companion to an employer plan such as a 401(k). But if you earn too much money, you may not qualify to invest fully — or at all — in a Roth IRA. And no matter how much you earn, you may find that contribution limits prevent you from building as fat a fund as you’d … [Read more...] about Through the back door to bigger retirement savings