rosversion: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/rosversion - from package: python-rospkg

You may install the required package with command yum install {package}

Error in other languages:
rosversion: bevel nie gevind nie
rosversion: comandă negăsită
rosversion: comando não encontrado
rosversion: commande introuvable
rosversion: command not found
rosversion: käsku ei ole
rosversion: không tìm thấy lệnh
rosversion: komanda nerasta
rosversion: Kommando nicht gefunden.
rosversion: kommandot finns inte
rosversion: komut yok
rosversion: nie znaleziono polecenia
rosversion: níor aimsíodh an t-ordú
rosversion: no se encontró la orden
rosversion: no s'ha trobat l'ordre
rosversion: opdracht niet gevonden
rosversion: parancs nem található
rosversion: perintah tidak ditemukan
rosversion: príkaz nenájdený
rosversion: příkaz nenalezen
rosversion: команда не найдена
rosversion: командата не е открита
rosversion: 命令找不到
rosversion: コマンドが見つかりません