The rosebud won't light. Acetylene/O2 burns twice the rate of propane, and you can't get the propane/oxygen out of the rosebud tip fast enough for it to stay lit.
You can light the rosebud with propane, no oxygen - but as soon as you turn on the oxygen, it will blow out the flame.
You're not going to get the pressure up high enough so it's useless with propane.
I don't use a propane torch to heat anything excpt glass