I don't think Roosevelt was talking about any one person or group in particular. He was staunchly advocating English and the national language and apparently believed that if an immigrant were not to learn English that he or she would not fully embrace or convert to "the American way of life." In my opinion, while an educated man, he held to certain jingoistic beliefs, one of which was that the immigrant had to fully assimilate the "American" culture or leave. He was apparently concerned about the "purity" of the gene pool and was a believer in eugenics, where undesirable traits such as indigence, low intelligence and other such things should be bred out of the pool. You can find hints of this in his speech at the Sorbonne in Paris, 1910. I don't know that he was necessarily a racist, but believed it was the duty of the "right" people to produce children to perpetuate the development of the human species. A great man to be sure, but deluded in some areas as well.