Can I voluntarily fail the roll for the Collapsed Room?
No, not in this situation.



You don't roll when entering a previously-discovered Collapsed Room. From page 6 of the rules,


  Only the explorer who first discovers the Collapsed Room needs
  to make the Speed roll listed there. Thereafter, any explorer
  entering the room can either ignore the room ability or use it
  intentionally, in which case that explorer still takes the damage.
  Falling to the basement doesn’t count as moving a space.


In this situation, however, your character wouldn't choose to jump down. They do not want to get further away. They are compelled to reach the room as fast as possible.



Gendolkari's answer makes no sense. They say one can choose to fail the roll, but then follows up with the rule saying one doesn't even get a roll.