This force caddy renew the certificates:
snap stop rocketchat-server.rocketchat-caddy
# in "/root/snap/rocketchat-server/current" remover a pasta .caddy que contém os certificados
sudo su
cd /root/snap/rocketchat-server/current
mv .caddy .caddy.bak
# Ao statar o serviço o Caddy gerará nova pasta com novos certificados
snap start rocketchat-server.rocketchat-caddy