THE COUNTER TO ROO'S IS A PUMA!!!
The reason they don't start in the roo, or any other transport, is because in the launcher once you place your troops in the carrier and press accept army, they bug out and have their number set to "0" instead of "1". So you have to drag them out, then back in, then right click again and they will work.
Actually im pretty sure its a launcher logic screwup. Feels like the launcher is telling the game
create infantry 'y', place infantry in halftrack 'x', halftrack 'x' does not exist, infantry 'y' can't start in halftrack 'x', create halftrack 'x'
How it should have worked is create halftrack 'x', create infantry 'y', place infantry 'y' in halftrack 'x'