The roamio remote will work in IR mode with the mini. Only some tivo remotes are learning ones....
The only functions that learning tivo remotes can learn are power, volume, input toggle and mute. It might be possible to trick the remotes input fuction to learn a tv remotes sleep command, if pressing one button on the tv remote cycles through the sleep time options.
I dont have a roamio (yet), but i dont think the stardard roamio remote is a learning one?
-Roamio Pro *Just out of the box!* :D
-Premier Xl4 MOCA bridge w/Slide Pro
-Mini Lifetime MOCA
-Comcast/TiVo Mutant dvrs - RIP
-2x Upgraded Series 2 - Retired