The first time Roain found out

Roain came upon the true that his best friend Oswin was suffering from paralysis and that he'd die in a couple months time because they couldn't travel for the treatment.
Oswin still wanted to live but knew Roain would sacrifice everything to find a cure so he kept quite till the day he couldn't physically hide it from Roain anymore and even after being found out he still put up an act to undermine the condition.

Thus starts their three months of struggle to find a way to get treatment before Oswin's time runs out