Is ring-around the rosies really a death song?

yes ring around the Rosie is a death song if you listen to the song the part that says a pocket full of posies posies is a flower they put in your coffin so u still smell good and ashes ashes we all fall down means a burning house and every one in the house dies.

It is also about the Black Plague

One of the first signs was red rings surrounding a rosey bump. Hence "Ring around the rosey,". "Pocket full of posies," Some people may have carried around pockets full of posies because the stench was so bad. Some also thought that it could cure them. "Ashes, ashes" is due to the tremendous numbers of dead people, which bodies were burned. "We all fall down." Do you really need an explanation for that one?