Pretty sure Dave confirmed at some point that the Shield was Punk's idea but it was Ambrose, Rollins, and Hero. They put Roman in and (per Punk) anyone who was in the ring with the Shield was told their role was to make Roman look as good as possible.
Roman certainly has all the rights to feel a certain kind of way about Punk, but him going off like that just comes off as someone trying to convince everyone that they are definitely Not Mad at someone.
Plus it makes Tony Khan look smart, why pay to hype up Punk's return when you can get the top star of your competitor to do it for you?