what was this role?
The residential schools were administered by Christian churches.
Canadian Indian residential school system
In Canada, the Indian residential school system was a network of boarding schools for Indigenous peoples. The network was funded by the Canadian government's Department of Indian Affairs and administered by Christian churches. 
where did residential schools take place in canada Such schools in Canada were mostly meant for the Indigenous Indians and were located at substantial distances from the Indigenous communities. was the government involved in this? Yes, the Department of Indian Affairs was responsible for this. how was language/culture getting affected by it? The schools aimed at suppressing the language and culture of the natives . As a result majority of the Indigenous languages existing today are "under serious threat of extinction". did anyone express any kind of sorrow regarding this system? The Vatican released an official expression of sorrow on the church's role in residential schools.
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Canadian Indian residential school system [SEP] Introduction
In Canada, the Indian residential school system was a network of boarding schools for Indigenous peoples. The network was funded by the Canadian government's Department of Indian Affairs and administered by Christian churches. The school system was created for the purpose of removing Indigenous children from the influence of their own culture and assimilating them into the dominant Canadian culture, "to kill the Indian in the child." Over the course of the system's more than hundred-year existence, about 30 percent of Indigenous children (around 150,000) were placed in residential schools nationally. The number of school-related deaths remains unknown due to an incomplete historical record, though estimates range from 3,200 to upwards of 6,000.