Toronto critic Robert Everett-Green described his style as a "fusion of Ontario fiddling traditions with the kind of architectural, string-crossing music of Bach's solo violin works." Schroer's music also frequently employs violin harmonic and double stop techniques to create distinctly modern sounds.
Schroer taught and mentored intensively in Smithers, British Columbia, in the Canadian Pacific Northwest over the last seven years of his life. He wrote a tune for each of the young people he taught – 59 in total – and recorded the tunes with Emilyn Stam, a young pianist from Smithers. His album Smithers is a thank-you album recorded for Smithers.
As a music educator, Schroer developed The Twisted String, a series of squads of young fiddlers and other musicians. Schroer composed the music for these groups.
His album Camino was recorded in churches along the Camino de Santiago pilgrim trail. Schroer walked 1,000 km of the trail in 2004 with his wife and two friends, carrying a portable recording studio. To save weight, he did not bring a violin case. He carried his instrument wrapped in a sleeping bag in his backpack, "like my own precious relic, carefully packed in its reliquary of socks and underwear." The album features solo playing, occasionally against a background of local sounds such as church bells, birds, and monastic voices.
In 2007, Schroer was diagnosed with leukemia, which proved to be untreatable.
A tribute concert for Schroer was held on February 19, 2008 at Hugh's Room in Toronto. It featured the Twisted String Project, seventeen kids, aged 9 through 18, led by two of Oliver's students. They raised the money through private donations to fly to Toronto from the B.C. coast, just so they could take part in the concerts. CBC recorded the concert and it was broadcast on CBC Radio 2's Canada Live on April 7, 2008.
Schroer's last concert was performed on June 5, 2008. In a letter to his fans on April 30 when he first announced his intention to do this concert, he called it ‘Oliver’s Last Concert on his Tour of this Planet’. He asked that his sold-out audience clap, not cry, and apologized for not being his normal glad-handing self; the risk of infection from personal contact would have been much too great. The subsequent Globe and Mail review called Schroer, an investigative fiddler.
During his final illness, Schroer said of his compositions, "I used to write a lot of jigs, reels and waltzes - as a matter of fact I still do. But over the years new kinds of melodies emerged - more rarefied, harder to pin down. There were prayers, incantations, whimsies, melismas, mysteriosos, heisenbergs, fractal reels, forest blues, blessings.... They are not so much entertainment tunes, but music that expresses other important things about my relationship to life. This music is, dare I say, more spiritual.
Schroer composed his final piece of music, Poise, on July 2, 2008. He died the following morning as a result of his leukemia. His last words were, "Well, I guess no excursions today."
Three months after his death, Schroer's CD Hymns and Hers was nominated for four Canadian Folk Music Awards: