re: muni and corporate bonds?

Bonds rates are low, yes, but rates work inversely with value. If the rates start picking up again, bond values drop.

As others have noted, having a muni in a Roth seems not very smart since Roth gains are tax-free anyway. That said, if you wanted to invest in a muni bond issue that people think is risky a Roth might be the place to do it. Detroit general obligation bonds, for example. If Detroit's bankruptcy works out the bonds could jump hugely. Or you could lose everything. That kind of volatile security is what you want in a Roth.