I am not sure if you should see the rogues as a single faction, but rather as various groups of bandits, monsters and undead.
Off course a GM could perhaps play as if he represents all those different kind of groups, but i don't know if that is feasible.
Its hard to be consistent for the GM's rp especially if he doesnt know where you got caught and how.
I wonder if rogues can read or write in the first place, since bandits are peasants and the monsters and undead are, well, monsters and undead...
They do offer you the ransom to pay if iam not mistaken which is questionable already, must be quite the intelligent monsters/undead to figure out what numbers are and what number a prisoner is worth.
If you could imagine all those problems away i still see a problem of people complaining about the GM, freeing certain characters while letting others rot.
Unless the exhange of letters is just flavour or rp.
