I found this notice to be helpful: Miscellaneous Pension Protection Act Changes Notice 2008-30http://www.irs.gov/pub/irs-drop/n-08-30.pdf
While it doesn't specifically mention inheriting from a qualified plan, it does discuss rollovers to a Roth from a qualified plan.
Prior to amendment by PPA ’06, § 408A of the Code provided that a Roth IRA could only accept a rollover contribution of amounts distributed from another Roth IRA, from a nonRoth IRA (i.e., a traditional or SIMPLE IRA) or from a designated Roth account described in § 402A. These rollover contributions to Roth IRAs are called “qualified rollover contributions.”
Subject to the limitations described in the final sentence of A-1 of this notice [income limits, since repealed, I think], the new definition of qualified rollover contribution in § 408A(e) includes distributions from annuity plans described in § 403(a) and (b) and from eligible governmental plans under § 457(b).
402(c)(11) is what says an inheritance by a non-spouse from an eligible retirement plan transferred to an IRA is an eligible rollover distribution (subject to direct trustee-to-trustee transfer). 408A(e) says that a rollover from an eligible retirement plan is a "qualified rollover contribution" to a Roth. At least I think that is what all this says.
(1) In general
The term “qualified rollover contribution” means a rollover contribution—
(A) to a Roth IRA from another such account,
(B) from an eligible retirement plan, but only if—
(i) in the case of an individual retirement plan, such rollover contribution meets the requirements of section 408 (d)(3), and
(ii) in the case of any eligible retirement plan (as defined in section 402 (c)(8)(B) other than clauses (i) and (ii) thereof [this excludes IRAs]), such rollover contribution meets the requirements of section 402 (c), 403 (b)(8), or 457 (e)(16), as applicable.
For purposes of section 408 (d)(3)(B), there shall be disregarded any qualified rollover contribution from an individual retirement plan (other than a Roth IRA) to a Roth IRA.