Okay kiddo, let me explain what are Royal Air Force roundels!
The Royal Air Force is the part of the British military that flies planes up in the sky. And, a roundel is a special symbol that they use on their planes to help them identify each other and tell them apart from the planes of other countries.
Now, imagine a big circle with colors in it. The roundel has a big red circle in the middle, surrounded by a thin white ring, and then a big blue outer ring. These colors are very important and have a special meaning.
The red circle represents the blood of the soldiers who died fighting for their country. The white represents the purity of their intentions, and the blue represents the sky they fly in and the loyalty of those who serve in the RAF.
Oh, and here's a fun fact - the roundel on the British flag is actually the same one used by the Royal Air Force. Cool, huh?