The roamio remotes are all RF and IR. The remotes that come in the box can do both, but by default they use RF to control the Tivo and IR to control your TV/sound system. The Tivos will respond to both RF and IR commands. I have a universal remote that uses IR and it works fine with the Roamios and Tivo minis.
The new Tivo Minis (TCDA93000) come boxed with the same remote as the Roamios and are both RF and IR. The older Tivo Minis (TCDA92000) come with an IR remote in the box, but you can get a USB dongle and RF remote for them.