Student or Learner
Next, I fell off/from the roof while repairing it but I sustained only superficial wounds and no fracture.
Which boldfaced word should I use? I think it should be 'off'.
They're both possible. However, if they are used in the reply to a question, then it would depend on the question.
Where did he fall from?
He fell from the roof.
What did he fall off?
He fell off the roof.
In my opinion, one uses the phrasal verb "to fall off" and the other uses the standard verb "to fall" followed by a preposition followed by a noun (making a prepositional phrase). I would break down the different versions like this:
He / fell off / the roof.
He / fell / from / the roof.
PS - no fractures
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.