Rodrigo penned a four-year deal when he joined Los Che permanently form Benfica in 2015 following a season-long loan spell.
The 26-year-old has been in superb form this term, scoring eight goals in 13 matches across all competitions – a return that has earned him a call-up to Julen Lopetegui's Spain squad.
"The best is yet to come," Rodrigo told Valencia's official website.
"One must have ambition to improve and grow. I still have many years of football ahead and what I want the most is to keep doing things well, to continue helping the club and to make everyone happy."
Rodrigo has the ideal opportunity to do just that when Valencia host Barcelona on Sunday, with the chance to trim the leaders' four-point advantage at the summit.
"It's an important game. It's always special when it is the leaders," he added.
"We are in a very good moment and they are too but we have to be confident to go out and face them in the game."