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/Slide Pro
-Stream (Gotta go unplug the sucker one of these days!)