This settlement actually started around 1903 before the railway came through. The settlement had no name, though, until the Grand Trunk Pacific Railroad pushed through and the population began quickly rising. Eventurally, the settlement was being referred to as "Eden". Officially, however, the name was changed to LeRoss, after the paymaster of the Grand Trunk Pacifi Railroad, L. E. Ross.
Back when the Grand Trunk Railway Company was planning a western expansion of their establish rail system, an unknown person devised an alphabetical naming scheme to name all of the un-named stations and lines, starting in Manitoba, cycling five full rounds of the alphabet, and starting a sixth before finally ending at Prince Rupert, British Columbia. LeRoss is part of the second cycle, situated between Kelliher and Mostyn (which actually named itself, Lestock).
Grand Trunk Pacific Railroad went out of business in the early 1920's. The railroad was taken over by the Canadian government and was made part of the Canadian National Railroad which is very active to this day.
Here's a link to some resources regarding the history of LeRoss:
Historic aerial photo of LeRoss in the 1950's
Our Treasured Heritage: LeRoss and Districts