Ironically, I received and installed my TiVo Roamio and TiVo Mini units just last night.
To answer the questions for anyone else that may be wondering.
The FiOS Coax network that runs through your house is already a MoCA network. This means that you will be able to setup with ease. Simply plug-in the Roamio in to the Coax and select the MoCA network when asked. When hooking up the Mini's, you select to run on MoCA as well. It all just worked. No additional adapters or devices were needed.
As for the Cable Cards - I already had a M-Card, so I didn't need to get any new ones. However, I did have to call Verizon to have them pair it with the new box. After pairing it, we have to force a Network Connection on the TiVo unit (where the TiVo contacts their servers and gets updates) twice. After doing this, it worked perfectly.
Do not select to have the TiVo create a MoCA network, or else you'll disconnect your local network (too many collisions). If you do this accidentally, simply go back to the TiVo and change it back to use an existing MoCA network and your network will come back almost instantly.