install cwrsync Or CYGWING

Use this link for CWRSYNC

Or install Cygwin and select RSYNC, SSH et openSSL package

Setup a DOS script:
C:
cd c:/Program Files (x86)/cwRsync/bin
rsync.exe -aivz --rsh="./ssh.exe -i C:/Users/bob/.ssh/id_rsa -p 8888" "/windows/backup/" "bob@backup.server.com:/var/backup"

the rsh command allow you to customize the connection particularly to change the default port (the -p option) and to point the right identity file (private rsa key) (the -i option)

for basic explanations please refer to rsync.net