It was during a canoe trip to Algonquin Park with his dad: “We were paddling down some little creek and he’s singing ‘Up on Cripple Creek’ to me and that’s the Band for me,” Roher, now 26, says in an interview.

“That’s where the Band lives for me, although I didn’t know it was the Band at the time. When I was a kid, it was like a camping song. It was only later that I was able to explore the depth and breadth of the body of their work and just how extraordinary those songs are.”

His early fascination with such Band classics as “Up on Cripple Creek,” “The Weight” and “Chest Fever” led Roher to seek to make a documentary out of Testimony, the 2016 autobiography of Robbie Robertson, the Band’s guitarist and lead songwriter.

Roher looks like a young Robertson, with eyeglasses and facial hair similar to what the rocker sported in his early days with the Band in the late 1960s and early ’70s, when the group members were evolving from unknowns into superstars as Bob Dylan’s backing musicians.

With Robertson’s blessing and participation in the project, Roher was able to attract backing that includes such film and music heavyweights as Scorsese, Ron Howard, Brian Grazer, Randy Lennox and Peter Raymont.

It was a true brotherhood until it finally wasn’t. The group was ultimately broken down by the rigors of the road and the rages of chemical addictions, petty jealousies and personal tragedy. A depressed Manuel committed suicide in his Florida hotel room in 1986, when the reformed group was touring without Robertson

Roher says Once Were Brothers isn’t so much the story of the Band as it is of Robertson’s fond memories of the group he departed in 1976, following a star-filled musical celebration called The Last Waltz, filmed by Scorsese, whose 1978 doc of the same name is also screening at TIFF.

“This is the story of the Band through Robbie Robertson’s eyes. It’s his truth, and it’s very important that people understand the difference there and that’s just something that I had to lean into. I was making a film about Robbie Robertson.”

Roher elaborates on this, on how the Band’s brotherhood broke down and on the indirect assists he received from Hudson, the only other surviving Band member, and the media-shy Dylan:

Film as mirror of events in Robbie’s book?

I like to say that it’s a spiritual adaptation of the book. The book was my source material, but I didn’t let it confine the film, or where I thought the film should go or where the storytelling should go. But for me, as a filmmaker, the book was such extraordinary inspiration as source material. Robbie tells the story best in his own words and, for the best possible movie, why would I deviate too far from that?

Robbie regrets about relations with Levon?

That’s what this film is about: these five guys who made something together that inspired me and millions of other people so profoundly. It’s about these five fragile young men, who are trying to do their best, who are struggling against their insecurities and their problems and their demons — and all of that goes into this music. That’s what my film is about and what I think we need to understand and celebrate.

Depicting the drug and alcohol dependencies?

The chemical addiction issues that existed within that group were just devastating. Humanity is something that was very important for me to put into the film. We have to collectively destigmatize addiction and mental health issues. In the ’60s and ’70s when the Band was operating, there was no lexicon to describe addiction or alcoholism as a mental health issue. It was, “Oh, he’s being irresponsible” or “He’s not fulfilling his end of the bargain.”

Garth Hudson, the Band’s keyboards wizard?

I had a fever-dream weekend where I went to Woodstock and I met with Garth. I sat down and I dined with him and listened to him. And although we did shoot an interview with Garth, I felt that his ideas and his thoughts would be better communicated, and the emotionality of Garth would be better addressed, through his music and through archival interviews that we found.

Trying to contact Dylan?

Oh, absolutely. Dylan and his office were really important to us and our story. Bob — Mr. Dylan — doesn’t like to do interviews, which I appreciate. But they helped us in other ways. They gave us open access to his archives. We found things and have material in the film that no one’s seen before. They were incredibly gracious throughout the film. My understanding is that Dylan has seen the movie and he really liked it. And that’s cool.

Biggest revelation?

That being in a band is hard. Being in a band is like nothing else. I’ve never been in a band. I grew up making films and drawing a lot, and it’s a different kind of thing. Being in a band, it’s like you’re married to five guys. That’s an analogy people talk about that’s often shared. And being in a band is impossible! It’s like you’re 16 years old and then, 15 years later, you’re still with the same group of guys! It’s like nothing else. And that’s what really came into focus for me.

Robbie Robertson’s account of the Band–Reliable?

The Band had five guys with five different memories and five different perceptions of what happened. This is Robbie’s truth. Do I verify it as much as I can with the people who where there? Absolutely. But at the end of the day, everyone has a different perception of what happened. No one was standing behind these guys taking notes. Nobody thought Music From Big Pink would be talked about and listened to and celebrated 50 years later. They were just five young men, my age, trying to do the best that they could in extraordinary circumstances.