There is a homebrew port of Sonic Mania for the Wii U, but it requires files from your own PC copy to run. Sonic R can be played on the Wii U via a Gamecube VC inject of Sonic Gems Collection. Hope this helps!

Clint, you can also try a Sega Saturn emulator for Sonic R, albeit you would either have to sacrifice your sanity to get it to fully work (Retroarch) or sacrifice Gamepad controls (Yabause Wii Port, you'll need to run it on a vWii.)