In your situation, you fall into the IRS created "ambiguous zone" with respect to isolating basis between a TIRA and a Roth IRA. This was created by Notice 2009-68. Since 2009, there have been several requests from major employee benefits firm to the IRS to clarify their intent. Nothing has been forthcoming and for 3 years now many employees have been doing twin rollovers (Pre tax to TIRA and post tax to Roth) and the plan administrators have not been directed by the IRS to change 1099R reporting, and therefore those twin rollovers are pretty secure.
The 1099R programming cycle for employer plans begins around November, so the IRS has another 10 months or so to potentially issue directives for change. For that reason, it is safer to do these rollovers after November when it's too late for the IRS to change instructions, than to do it now when the IRS has 10 months to determine what they will do for 2013. That said, there is not too much to risk even now in rolling the after tax check to your Roth IRA, with the intent to report it as a tax free Roth rollover on line 16b of your 1040. The 1099R for it will show no taxable amount in Box 2a. If the IRS rules against you in the meantime, you have until 10/2014 to recharacterize a 2013 rollover (conversion) back to a TIRA. That said, if this were to happen, then you have 8606 basis in your TIRA that can only come out pro rata, and some people would not want that compared to simply keeping the after tax amount as taxable savings.
GIven the ACA and everything else the IRS has on their table now, I would be inclined to do the rollover to the Roth IRA since the potential benefit exceeds the risks.