William Allen Van der Roest was born in Canada in 1913. At some point in his life, he came to live in New York City (specifically, 228 West 111th Street in Harlem), and at the age of 24, he decided to enlist to go fight in Spain. After obtaining a passport on March 29, 1937, he left New York aboard the Aquitania (an ocean liner that was sailing from New York to Cherbourg and Southampton) just 2 days later. Following his arrival in Spain (presumably coming from Cherbourg along with several other volunteers who also departed New York aboard the Aquitania on March 31st) in April, he eventually became the secretary of his company within the Lincoln Battalion.
On July 6th, 1937, the Lincoln, Washington, and British Battalions were sent to serve as part of the offensive at Brunete against the Nationalists. They were sent to capture the town of Villanueva de la Cañada and ended up spending the entire day engaged in a brutal struggle that was ultimately inconclusive. They were sent back to break the stalemate at the town the next day, and although they did manage to take the town, they suffered heavy casualties. Among those casualties was Van der Roest, who was killed during an attack by Nationalist aircraft. His demise was personally witnessed by Carl Syvanen, a fellow member of the Lincoln Battalion who would go on to recount the story in the Finnish novel Meidän Poikamme Espanjassa (Our Boys in Spain).
Interestingly enough, Van der Roest is claimed as a member of both the Lincoln Battalion and the Canadian-centric Mackenzie-Papineau Battalion: he was killed before ever getting the chance to join the "Mac-Paps" (as Syvanen later would) but is still listed among those Canadians who gave their life in service of the Republic (it is unclear whether or not he would have wanted to be remembered as a Canadian or an American, but his hometown is still remembered as New York).
Rosenberg, Leo. “Brunete The Good And The Bad.” The Abraham Lincoln Brigade Archives, http://www.albavolunteer.org/2018/02/brunete-the-good-and-the-bad-by-leo-rosenberg/. Accessed 29 Apr. 2020.
“Bernard Entin.” The Abraham Lincoln Brigade Archives, https://alba-valb.org/volunteers/bernard-entin. Accessed 29 Apr. 2020.
“Carl Ralph Syvanen.” The Abraham Lincoln Brigade Archives, https://alba-valb.org/volunteers/carl-ralph-syvanen/. Accessed 29 Apr. 2020.
LIFE. Time Inc., Feb. 1937, p. 9, https://books.google.com/books?id=tUsEAAAAMBAJ.
“The Volunteers.” The Friends and Veterans of the Mackenzie-Papineau Battalion, http://www.web.net/~macpap/volunteers.htm. Accessed 29 Apr. 2020.
“VAN DER ROEST, William Allen.” University of Barcelona, http://sidbrint.ub.edu/ca/content/van-der-roest-william-allen. Accessed 29 Apr. 2020.
“William Allan Van Der Roest.” Social Sciences and Humanities Research Council of Canada, https://spanishcivilwar.ca/volunteers/william-allan-van-der-roest. Accessed 29 Apr. 2020.
“William Allen Van Der Roest.” The Abraham Lincoln Brigade Archives, http://www.alba-valb.org/volunteers/william-allen-van-der-roest. Accessed 29 Apr. 2020.