1 Mafia 1-Shot Ninja
1 Mafia 1-Shot Rolestopper
1 Mafia Encryptor
vs.
1 Weak Doctor
1 Roleblocker
8 Vanilla Townies
Moderator QT
Dead QT
Mafia QT
The Mafia 1-Shot Rolestopper cannot kill and rolestop in the same Night. As far as I can tell, there are no confusing interactions between the Rolestopper and the Roleblocker because of this.
If the Weak Doctor targets a Mafia member, but is roleblocked or rolestopped, then the Weak Doctor will not die.
The Mafia 1-Shot Ninja is a complete red herring, and affects nothing in the game.
The core idea behind this setup is to have somewhat unusual power roles who have a chance to interfere with each other. The Weak Doctor is less powerful than a Cop, in that the results are less trustworthy; I believe that a competent Weak Doctor will realize this, especially if the Roleblocker or Rolestopper flip. The compensation for this reduction in investigative power is that the Mafia have no counter to the protection ability other than attempting to kill the Weak Doctor. The Roleblocker's power is limited in comparison, but does gain significant usefulness in the event that only 1 Mafia member remains.
The Encryptor doesn't really play into this dynamic, but it does give the Mafia a boost in the day game, since their night game is relatively weak.