You mentioned MoCA, but if you connecting your Roamio and Mini to your ethernet, there won't be any need to run MoCA.
Other than that it sounds like you should be good.
You didn't describe which Roamio you have but the plus and pro models can bridge Moca so later if you want to add another mini and can't connect it to your router by ethernet, you will be good to go, if you have the base model Roamio then in the future you might need a MOCA adapter but as you describe what you have now, you don't need to setup a MOCA network on your coax cable.
TiVo Roamio Pro
TiVo Roamio Plus (3tb)
TiVo Mini (three)