The old Tetris app stopped working for me too. I scrolled through the 398 'available games' and near the end of the list I noticed a slightly different version of Tetris - I grabbed it. Its free with ads, or 4.99 w/no ads. Its decent, not as refined as the original Tetris on the Roku, but it functioned ok. One note, the D-Pad is used with the controller in a vertical position whereas the original game allowed you to turn the controller 45 degrees and hold it like an oldschool gamepad.
This new version also doesn't allow you to swap the current piece for the piece that is 'up next'.
The old app was a 5.0 for me. This new version is probably a 3.5 due to the controller config, no swapping of pieces and the music seems a little odd vs. the original.