what do KH Rollo Disks do
http://www.unicycle.uk.com/unicycle-parts/cranks/crank-fittings/kris-holm-rollo-discs.html
They give you more room to place your foot on the crank during rolls.
Some “flatland” tricks involve standing on the crank. This is made easier if the crank width is extended creating a bigger area for your foot to stand on. A bit like having axle pegs on a BMX, except the pegs in this case are the extended cranks of your unicycle.
Hope this helps.
they are a pain 
jk
Keep in mind if you are NOT doing flatland tricks they may get in the way. For instance, if you are jumping and/or riding skinnys you may find you hit the rollos with your shoes on most revolutions. You can adjust to this but need to think about it.