The 25-year-old centre-forward has joined West Brom from Russia Premier League club Zenit.
Witsel hopes that his now former teammate Rondon succeeds in the Premier League with West Brom.
Busy summer for West Bromwich Albion
West Brom have been busy so far this summer in the transfer market, with former Malaga and Rubin Kazan star Rondon being their fifth signing since the end of the 2014-15 campaign.
Winger James McClean, defender James Chester and striker Rickie Lambert have arrived from Wigan Athletic, Hull City and Liverpool respectively, while winger Serge Gnabry has moved to the Baggies on a season-long loan deal from North London outfit Arsenal.