let's look at it this way, you have 7 chace to do that 10% due to the 7 hit ko from togekiss, 1 turn out of 2 have to be spent roosting, so you go to at least 14 chance of that 10% now, on the roost turn the lanturn regain hps form leftover, so you add a few extra turn of Tbolt, no need to run the exact calculation but quickly: let's say 20 turn ko and that's 87.9% total chance to paralyses eventually, by then it would also run out of roost pp, just saying