Why do pilots say ‘Roger’ – not Everyone in WWII could speak English

Even if you haven’t heard it in real life, I’m guessing you’ve heard a pilot on TV say “Roger.” I bet you’ve even heard pilots say “Roger Wilco.”
Have you ever wondered who Roger Wilco is? And why pilots like to say his name?

According to The Straight Dope, in 1927 “Roger” was the word chosen to represent the letter “R,” which is, of course, the first letter in the word “received.” In other words, a pilot would receive instructions, and to indicate he had received them, he’d say “Roger.” Why didn’t he just say “received”? Well, during WWII, not everyone spoke English, but “R” — or “Roger” — became the internationally accepted way of acknowledging receipt of instructions. (Of course, in 1957 the word “Roger” was replaced with the word “Romeo” but by that time, “Roger” and “received” were synonymous.)
So what about “Wilco”? Its story is even simpler: it’s an abbreviation of “will comply.” So when pilots say “Roger Wilco,” what they mean is “I received your instructions, and I will follow them.”
Roger?
SOURCE http://www.thevintagenews.com/