I know someone posted the link in a recent post. I couldn't find that post in a search with different search terms. But I found a different post that led me to the Roamio User Guide. I figured I'd post the links with some of the different search terms I used, so that other people who are doing a search may find the guide links more easily.
Roamio User Guides - Main Page
4-Tuner Roamio Start Here Poster (PDF)
Roamio Plus/Pro Start Here Poster (PDF)
Instructions for CableCARD Installers
(Roamio User Guide, Roamio Viewer Guide, Roamio Viewer's Guide, Roamio Instructions, Roamio Instruction Guide, Roamio User Manual, Roamio Instruction Manual)
Feel free to add your own search terms to the thread. Hopefully, this will be helpful. Personally, I wish TiVo still shipped out old-school instruction manuals with the Roamios.